5. Optical Components and Hardware
This section describes the optical components and mounting hardware used in the LHC project. Lasers are covered by their own section, but associated optics are described here. Hardware is included for all experimentation as well as the final layout.
1. Apertures/Pinholes
2. Attenuators
3. Beam Expanders
4. Beamsplitters
5. Diffusers
6. Faraday Isolators
7. Filters
8. Lenses
9. Mirrors
10. NLOs
11. Q-Switches
12. Waveplates/Polarisers
13. Prisms
14. Visualisers
15. Windows
16. X,Y,Z Mounts
17. Optical Breadboard
1. APERTURES (PINHOLES)
Intended to be added to laser resonators to produce TEM00. Also useful for limiting laser energy into PT detectors. The ceramic ones were only $2 each, bought for experimentation.
Lenox Laser's website contains useful information about the materials used in their own range:
http://lenoxlaser.com/products/optical-apertures/high-power-apertures
Material Properties St.Steel Copper Tungsten Molybdenum Ceramic Diamond
Melting Point (C) 1400-1450 1084 3440 2620 2050 3550
Boiling Point (C) N/A 2927 5555 4639 2980 4827
Reflectivity (%) 84 90 62 58 95 N/A
Damage Threshold (J/cm²) *2.3J 2-10 *3.1-6.5J 6-10 (GW/cm²)
Density (g/cm³) 8.03 8.92 19.25 10.28 3.88 3.51
Brinell Hardness (MPa) 170 874 2570 1500 107 N/A
Molecular Weight (g/mol) N/A 63.55 183.84 95.96 N/A 12.01
*These estimates for damage threshold were derived from [O38]: 'Conclusion: experimental single-pulse (*2.3J/cm² for SS and *6.5J/cm² for Mo) and multiple-pulse (*3.1J/cm² for Mo) damage thresholds were obtained.'
http://lenoxlaser.com/shop/optical-apertures/high-power-apertures/molybdenum-aperture
Molybdenum Apertures are most commonly used in the optical transfer assembly of an optical system using a powerful laser as a source. Lenox Laser Molybdenum apertures offer crisp edge quality without sacrificing high damage threshold, making these ideal for spatial filtering of powerful laser light sources.
http://lenoxlaser.com/shop/optical-apertures/high-power-apertures/ceramic-aperture
Ceramic Apertures are used in high energy applications and are intended to be used in the optical transfer assembly of a system using a powerful laser light source. These apertures are designed for shaping beams of high power lasers. A practical example is the aperture within a spatial filter assembly. For Q-Switching applications, consider a highly reflective aperture disc surface and a very high melting temperature disc material.
Potential uses for the LHC project:
Ti:S = 8.5mm rod ceramic aperture 7.0
Ruby = 6.0mm rod ceramic aperture 5.5
M580KK = 5.0mm rod ceramic aperture 4.8 + 4.6
Alexandrite = 4.0mm rod ceramic aperture 3.9 + 3.8 + 3.7
Nd:YAG = 4.0mm rod ceramic aperture 3.9 + 3.8 + 3.7
MK367 = 3.0mm rod ceramic aperture 2.9 + 2.8 + 2.7
ceramic pinhole aperture 7.00mm x 25.4mm dia Laser Sources UK AP25-7.0OP
ceramic pinhole aperture 5.50mm x 25.4mm dia Laser Sources UK AP25-5.5OP
ceramic pinhole aperture 5.00mm x 25.4mm dia Laser Sources UK AP25-5.0OP
ceramic pinhole aperture 4.80mm x 25.4mm dia Laser Sources UK AP25-4.8OP
ceramic pinhole aperture 4.60mm x 25.4mm dia Laser Sources UK AP25-4.6OP
ceramic pinhole aperture 4.00mm x 25.4mm dia Laser Sources UK AP25-4.0OP
ceramic pinhole aperture 3.90mm x 25.4mm dia Laser Sources UK AP25-3.9OP
ceramic pinhole aperture 3.80mm x 25.4mm dia Laser Sources UK AP25-3.8OP
ceramic pinhole aperture 3.70mm x 25.4mm dia Laser Sources UK AP25-3.7OP
ceramic pinhole aperture 3.00mm x 25.4mm dia Laser Sources UK AP25-3.0OP
ceramic pinhole aperture 2.90mm x 25.4mm dia Laser Sources UK AP25-2.9OP
ceramic pinhole aperture 2.80mm x 25.4mm dia Laser Sources UK AP25-2.8OP
ceramic pinhole aperture 2.70mm x 25.4mm dia Laser Sources UK AP25-2.7OP
ceramic pinhole aperture 0.85mm x 25.4mm dia Laser Sources UK AP25-0.85OP
ceramic pinhole aperture 0.80mm x 12.5mm dia Laser Sources UK AP12.5-0.8OP
2. ATTENUATORS
These are to attenuate the power of the beam feeding into optical sensors: PDs, PMTs and Cohu or
Lasercam CCD cameras for beam profiling. All use the standard lens 25mm C-mount except the ATP-SM which has a weird thread that looks to be around 19mm but no-one seems to have any adaptors at this size.
It's not listed in the large table of threads at wikipedia: http://en.wikipedia.org/wiki/Lens_mount.
It came with an adaptor that converts this to a female C-mount, but I need two male c-mount adaptors.
I tried to make an adaptor using polymorph material [G23] but it kept fragmenting. The next attempt will add PTFE film to the female adaptor and then try to mould a male thread using filler.
Another planned modification is to dril out the 3mm ends of the Newport 935-3 to 5mm instead because looking inside, the wedges are actually about 10mm wide. It looks to me like Newport uses the same design for 3mm and 5mm apertures and the only difference is the hole in case.
Continually variable beamsplitter
Special Optics Glan Prism + 1/2 waveplate beamsplitter 10mm Nd:YAG 1064nm 2.8J @ 30Hz
A Glan type polarising prism can be used with a half waveplate to adjust beam energy. This consists of a half waveplate followed by a polarising beamsplitter. By varying the rotation angle of the half wave plate you can control how much light of one polarisation is carried through, from 1% to 95%.
S-polarised light is reflected at 90 degrees while p-polarised light passes straight through. The 1998 laser paper 'lasers used in LA-ICP-MS' says LIBS needs power to be finely controlled and the recognised best way of controlling laser power is to use one of these.
Coherent 1098403 50J/cm² 50J max BCube 5GW/cm² 380nm-2.2µm 5% = 20 max
Coherent 00-3328-000 0.1J/cm² 10J max VARM OD filter 1W/cm² 380nm-2.2µm, 1:1 to 4x10^5 max
Photon ATP-SM 0.1J/cm² 10J max variable wedge 1W/cm² 380nm-2.5µm, 3x10^3 to 10^7.4 max
Newport 935-3 3J/cm² variable wedge 20W/cm² 200nm-2.1µm 0-20dB (= 1% = 100)
3. BEAM EXPANDERS/TELESCOPES
a. To match Nd:YAG beam diameter to 700nm laser diameter
b. UV beam expander to produce smallest focus
http://www.newport.com/n/focusing-and-collimating
'To get a tighter focus either increase the focal distance or increase the beam'; 'No improvement of the lens can yield any improvement in the spot size. The only way to make the spot size smaller is to use a lens of shorter focal length or expand the beam.'
1064nm Rodenstock LINOS 4401-256-000-20 3-8x 8mm in 30mm out 30J/cm² (Nd:YAG)
~700nm 630-830nm LINOS 4401-258-000-20 2-8x 8mm in 30mm out 30J/cm² (ruby)
248nm CVI BXUV-4.0-3X-248 Beam Expander 6J/cm² @ 7ns (final optic focus)
4. BEAMSPLITTERS
a. POLARISING BEAMSPLITTER CUBES
A polarising beamsplitter cube separates the p and s polarisation out to two beams 90 deg apart.
http://www.cvimellesgriot.com/Products/Laser-Line-polarising-Cube-Beamsplitters.aspx
'Polarising beamsplitter cubes are used to split a laser beam into two orthogonally polarised components; p-polarisation is transmitted straight through while s-polarisation is reflected at 90°. PBS polariser cubes utilize a durable all-dielectric coating at the internal cemented interface, and all external surfaces are AR coated for the wavelength specified. For best spectral performance and transmitted wavefront, cube beamsplitters should be used with collimated or near-collimated input light. The PBS and other cemented beamsplitter cubes are easy to mount, mechanically durable and ideal for use up to 1 J/cm² at 1064nm.'
a. To isolate P & S polarities,
b. To attenuate when combined with a polariser.
Pol. beam splitter cube 1064nm 0.5" cemented 'low power' OFR PSCL-13-1064-Z
Pol. beam splitter cube unknown 0.5" cemented 'low power' (for ruby laser)
b. BEAMSPLITTER PLATES
These split off a proportion of the beam, useful for beam power measurements.
1/100 beamsplitters 532nm 1% reflect 9.8 dia x 2 thk 45
C. HARMONIC BEAMSPLITTER PLATES
These split off laser lines, useful for isolating harmonics
T532nm & 1064nm / R266nm 25.4 dia x 6.35 thk 45 (to deflect 266nm UV to target) (2)
T532nm & 1064nm / R355nm 25.4 dia x 6.35 thk 45
.
5. DIFFUSERS
A diffuser disperses the Gaussian profile of a laser beam to a uniform circle of light.A use for this is to attenuate the beam for detection or power measurement.
Frosted glass to capture VIs image of UV beam for beam profiling camera
HE ND-Yag Opal Diffusing Glass 23mm to diffuse Nd:YAG for wavelength measurement
6. FARADAY ISOLATORS (OPTIONAL)
http://www.eotech.com/techsupport/faraday/userguide/lowerpower/lowerpower.php
'A Faraday Isolator is a cylindrically shaped magneto-optic device. Strong Neodymium Iron Boron permanent magnets are used to generate high (>10,000 Gauss) axially oriented fields within the magnet housing. This field causes 45 degrees of non-reciprocal polarisation rotation for propagating light via the Faraday Effect in the terbium gallium garnet ('TGG') crystal located within the magnet housing. In operation, the magnet housing is sandwiched between input and output polarisers that have their transmission axis oriented 45 degrees relative to each other to account for the 45 degrees of Faraday Rotation in the TGG crystal in the forward (transmission) direction. In the reverse (isolation) direction, the non-reciprocal Faraday rotation and the 45 degree polariser transmission axis angle add so that the polarisation transmitted by the output polariser is rejected at the input polariser.
Optical isolators are used mainly to preventing unwanted feedback affecting beam quality in precision instruments and to prevent reflections from lenses hitting the originating laser and causing it damage. A misaligned Q-switch can cause immense damage due to reflections that a Faraday Isolator can minimise. Coupling of a light beam into an optical element is always accompanied by unwanted feedback due to unavoidable Fresnel reflection at the interface. Such reflection has been successfully reduced down to a practically insignificant level by employing anti-reflection (AR) coatings of multi-layer dielectric films on optical surfaces. However, there are some situations in which an AR coating is not sufficient or inappropriate, and in my case some of my experimental optics are not AR coated.'
Got one for Nd:YAG but not one for the experimental DIY ruby, which is probably a far greater need.
Quantum/Continuum 1GW 1064nm GW? Dual isolator (for M580KK)
7. FILTERS
a. INTERFERENCE FILTERS
Passes only a narrow wavelength or range.
1064nm ±10nm to isolate flashlamp wavelengths (Omega filters)
700nm ±10nm to isolate flashlamp wavelengths (Omega filters)
b. BIREFRINGENT FILTER (EXPERIMENTAL)
A birefringent filter is typically used to tune lasers such as Alexandrite, Ti:Sapphire etc.
http://www.dtic.mil/dtic/tr/fulltext/u2/a257023.pdf
'A birefringent filter comprises one or more crystalline quartz plates, placed in the laser cavity at Brewster's angle. The plates are cut parallel to their optical axes, and their birefringence causes the linear polarization of the incident laser beam to become elliptical. Only one frequency will make a complete 180-deg (or multiple thereof) polarization flip: the polarization of all other beams rotates more or less than that.
The elliptically polarized beams suffer additional losses at other Brewster-angle cavity elements and fail to reach the lasing threshold. The free spectral range (FSR) of a multi-plate birefringent filter is determined by its thinnest plate and is typically 80 to 100nm. The FSR is the difference between adjacent eigen wavelengths (i.e., wavelengths that undergo a complete polarization flip). Rotating the filter around the axis normal to the plate changes its eigen wavelengths.
There are two types of birefringent filters. Each one is designed to optimize performance in a specific dye tuning range. The filter-plate thickness is chosen to maximize tuning linearity and wavelength discrimination and to minimize power loss through the tuning element. Additional plates sharpen the response of the filter by increasing its finesse. Each birefringent filter must be factory aligned for maximum tuning smoothness.'
Spectra Physics 3900 quartz Ti:S 3-plate birefringent filter 700 - 1000nm
c. LOW PASS FILTER
Need 694.3nm interference filter for ruby laser and bought (new) low pass 695nm filter for Lumenis medical laser. I assume it is BK-7, which will mean it should block 400nm and below, essentially a 400nm - 695nm interference filter.
Lumenis IPL Medical Laser Treatment Filter 695nm OP-003162 37mm x 17mm x 1.8mm
d. HIGH PASS FILTER
8. LENSES
WD = Working Distance
HE lenses must be air spaced - glue will break down
Achromats (ACH) are best for smallest focusable spot. Must be air-spaced for high power.
Plano Convex (PCX) next best
a. UV FOCUSING LENS
Sigma Koki lens: 'These lenses are manufactured with a synthetic fused silica material and it has a high transmittance value in the ultra-violet wavelength of 180 - 400nm. They have excellent performance and ideal for focusing and imaging applications. There is no adhesive or heat absorption material used to produce these lenses, they show high resistance to the ultraviolet light. They are made of 2 or 3 spherical lenses and they offer correction on spherical and chromatic aberration.
Standard focal lengths for Excimer laser with 248nm, 266nm and 355nm. NA 0.1 or below (ETL model NA 0.25) can be focused to the diffraction limit. **To reduce the focus spot size, ensure that the input beam diameter (1/e^2) is reduced to half of the effective diameter of the focus lens**. These focusing lenses are not chromatic lenses; they are not optically corrected. The lenses have 4% of reflectivity; therefore about over 20% of loss is expected in transmission.'
For my Sigma Koki ETL-30-60P UV lens: PUT THIS IN EQUATIONS
http://www.parallax-tech.com/faq.htm#technical
focal length = 59.7mm, lens aperture (i.e. Dia) = 27mm but they say need beam **half that = 13.5mm
For 213nm - DOF = 2.50 x 0.000213 x (59.7/13.5)² = 0.000213 x 956.0977 = 0.20365µm
For 213nm - Spot = 1.27 x 59.7 x 0.000213 x 1² / 13.5 = 5.61622' x 0.000123 = 0.001196mm = 1.196µm
Check: their worked example for CO2, f=100mm, D=6mm:
for 10.6um Spot = 1.27 x 100 x 0.01 / 6 = 0.2117mm = 200µm
For 193nm - DOF = 2.50 x 0.000193 x (59.7/13.5)² = 0.000193 x 956.0977 = 0.18453µm
For 193nm - Spot = 1.27 x 59.7 x 0.000193 x 1² / 13.5 = 5.61622' x 0.000193 = 0.001084mm = 1.084µm
'Values are calculated from the formula for spot size = 0.013 x f / D where D is beam diameter at lens position. 'D' may be increased 2 or 3 times by using a 'beam expander' which means spot size will be 2 or 3 times smaller BUT depth-of-field will be 4 or 9 times less.'
Spot Size and Depth Of Field for some standard lenses calculated for beam diameter of 7mm at lens position and M² = 1:
f Focal Length Spot Size Depth Of Field
mm = inch µm = inch µm = mm = inch
12.7 0.50" 23 0.001" 86 0.086 0.003"
19.0 0.75" 37 0.001" 200 0.200 0.008"
25.4 1.00" 49 0.002" 350 0.350 0.014"
38.0 1.50" 73 0.003" 800 0.800 0.030"
51.0 2.00" 98 0.004" 1400 1.400 0.050"
76.0 3.00" 147 0.006" 3100 3.100 0.120"
101.0 4.00" 195 0.008" 5600 5.600 0.200"
127.0 5.00" 245 0.010" 8800 8.800 0.340"
152.0 6.00" 290 0.011" 12600 12.600 0.500"
Uncoated 25.4mm dia PLCX UVGSFS (175nm - 2.0µm) experimental LHC final optic
Sigma Koki ETL-30-60P UV focuser FL59.7mm WD 52.4mm NA0.23 LHC final optic
b. IR OUTPUT LENS
For experimentation with prototype Nd:YAG:
1064nm 25.4mm dia PLCX 50-55mm FL in square metal holder
1064nm 25.4mm dia PLCX 76.6mm FL
25.4mm dia PLCX 100mm FL CVI 01-LQP-007 (S19-2-163A) UV
1064nm in 10.5mm brass focus mount for CW laser diode
c. FOR ARGON LASER
3W launch lens into 442-532nm fibre optic SMA input
Adjustable collimator for YAG/Argon fibre optic SMA output
d. BEAM SHAPING (TOPHAT) LENSES
I acquired 266nm tophat beam shapers to shape the final DUV beam, but one has no coating and presumably could be used on the fundamental 1064nm prior to the HG NLOs which may be a better overall solution.
Comment from the seller: 'The damage threshold is around 2J/cm², depends also on pulse duration. These were made for 20ns to 40ns lasers. However, I have used them down towards 10ns and lower.
I have a Gaussian to round flat top: Design 266 nm [No AR coatings], Design 266 nm [Thin AR Coatings], Design 266 nm [Thick AR Coatings]. The design is a shaper/compressor/collimator design; Incoming beam is designed for 5.6 mm 1/e² and output is 1.7 mm dia pseudo collimated. At 266 nm, the AR coating will help, 3% to 4%. I had a variety of coatings to test threshold survivability (Thin and Thick are AR stack design of the coatings).'
square 2Jcm² 20-40ns 6.5mm² to 5.6mm dia (no AR)
square 2Jcm² 20-40ns 6.5mm² to 5.6mm dia (266nm thin)
square 2Jcm² 20-40ns 6.5mm² to 5.6mm dia (266nm thick)
square 2Jcm² 20-40ns ?.?mm² to 1.7mm dia (no AR)
square 2Jcm² 20-40ns ?.?mm² to 1.7mm dia (266nm thin)
square 2Jcm² 20-40ns ?.?mm² to 1.7mm dia (266nm thick)
9. MIRRORS
Mirrors specified for a wavelength usually also reflect other wavelengths, but with less efficiency.
For example gold has a very high IR reflectivity of approximately 95%, but much worse below 500nm.
a. FOLDING MIRRORS / PHASE RETARDERS ?
1064nm 30mm x 22mm x 4mm thk rect. Coherent HE 45 AOI mirror
1064nm 30mm dia x 4mm flat '40W' Chinese HE 45 AOI mirror
A folding mirror swaps laser polarity 180 degrees.
b. HR / IC
Highly Reflective Input Coupler mirror for laser cavity. This sits at the rear end of a laser cavity and reflects all laser light back into the lasing medium. A concave HR with a wide ROC e.g. 40cm/75cm is typically used to ease alignment.
1064nm 8.0mm dia x 4.00mmm & 2cm curve Coherent HE 0 AOI
700nm 25.0mm dia x 6.35mm thk Coherent HE cavity folding AR range 690nm-835nm
694?? 22.0mm dia x 3.15mm thk 40J? in box marked HENE AR 694nm + 632nm
c. OC
Partially reflective Output Coupler mirror for laser cavity.
The OC has partial transmission and sits at the output of the laser.
The OC is the mirror through which the laser beam appears.
The amount of reflectivity / transmissivity depends upon the lasing medium and its pump:
1. CW pumped Nd:YAG rod has less doping to saturate quickly is lighter in colour, Transmissivity typ 99%
2. Flash lamp pumped Nd:YAG has more doping and is darker in colour. Transmissivity is typically 99%
3. Laser diode pumped Nd:YAG has more doping and is darker in colour. Transmissivity is typically 99%
4. CW pumped alexandrite rod has less doping to saturate quickly. Transmissivity is typically 99%
5. Flash lamp pumped alexandrite rod has more doping. Transmissivity is typically 99%
6. Flash lamp pumped Ruby has more doping. Transmissivity is typically 60%.
694nm 25.4mm dia x 6.35mm thk ROC1.00m 50% AR/AR Spectrosil B
700-800nm OC 0.5" x 3/8" 95% for Ti-Sapphire
d. LINE BANDPASS
Reflects a narrow band only, e.g. CVI Y1-2037-45 = 1064nm ±114nm
1064nm 50.0mm dia x 0.375" thk 45 ±114nm 950-1175nm CVI Y1-2037-45-UNP
488nm 25.0mm dia x ?? mm thk argon line mirror 0.1% tx @ 488nm AR range 450nm-500nm
193nm 37.5mm dia x 5.00mm thk 45 ± 18nm 175- 210nm ARC 193-FR45-1.5D-FL
e. ORDINARY MIRRORS
BBAR 12.7mm dia New Focus 5153 silver 0-45 AOI 0.5J/cm² 10ns 96% top adj mounts 450nm-12um (4)
10. NLOs
These crystals were bought over time. Some are in really good condition, others are not.
One assembly, #6 (omitted) was actually empty. Two crystals (3,7) are shattered, but I bought them at a low price for their motorised assemblies. Those marked 'ex-motor' were removed from similar assemblies:
# Manf Part# Harmonic λ dimensions Assembly Chem Type φ ph θ angle Notes
1 Continuum SHG-T-30 2nd (2HG) 532nm 11 x 11 x 30mm TT heater KD*P? I? 45°? 37.7°? ex-motor
2 Continuum SHG-T-25 2nd (2HG) 532nm x x 15mm TT Heater KD*P? I? 45°? 37.7°? ex-motor
3 Quantel SHG-T-30 2nd (2HG) 532nm 11 x 11 x 30mm TT heater (sliced) KD*P? I? 45°? 58.0°?/53.7°? motor assy
4 Quantel unknown 2nd (2HG) ???nm 10 x 10 x 20mm AT Round Blue D*CDA I ? 81.0° box says AT
5 CasixJDSU - 2nd (2HG) 532nm 3 x 3 x 3mm KTP (with MK580) KTP I? 90° 23.5°? xtal only
7 Quantel THG-T-30 3rd (3HG) 355nm 11 x 11 x 30mm TT heater (cracked) KD*P? II? 90°? 59.3°? motor assy
8 Continuum THG-T-2 3rd (3HG) 355nm 12 x 12 x 20mm NO heater D*CDA? II? ? ?? ex-motor
9 Unknown THG 3rd (3HG) 355nm 4 x 4 x 4mm TT heater KD*P? II? 90° 59.3°? 1+2->3HG
A Continuum FHG-T-? 4th (4HG) 266nm 6 x 6 x 6mm NO heater & UV BBO? I? 90° 47.6°? pins O/C
B LaserSrc* XQ13OP 4th (4HG) 266nm 8 x 8 x2.5mm xtal only & UV BBO I 90° 47.6° xtal only
C Quantel 5HG-3+2 5th (5HG) 213nm 7 x 7 x 5mm NO heater & UV BBO? I? 90° ? 2+3->5HG
I am assuming those with heaters are TT = Temperature Tuned, AT = Angle Tuned.
Anything with a ? is my guess based on data from various sources, including this Laser Sources (LaserSrc*) table:
http://www.laser-sources.co.uk/Harmonic-Crystals.php
Best are:
#1 2HG 11x11 (532nm), #A 4HG 6x6 (266nm), #8 3HG 12x12 (355nm), #C 5HG 7x7 (213nm)
2HG harmonic crystal to convert 1064nm to 532nm
3HG harmonic crystal to convert 1064nm + 532nm to 355nm
4HG harmonic crystal to convert 532nm to 266nm
5HG harmonic crystal to convert 532nm + 355nm to 213nm
SFM BBO crystal to convert 700nm + 266nm to 193nm (on my wishlist but $$$)
SFM BBO crystal to convert 2080nm + 213nm to 193nm (on my wishlist but $$$)
11. Q-SWITCHES
a. Active
b. Experimental
c. Mechanical
D. Passive
a. ACTIVE / POCKELS CELLS
Inrad Pockels cell NC-530A FC-43 1.064nm FOR Nd:YAG [measured 6.2pF]
Inrad Pockels cell 202-090 BBVIS FOR ruby [measured 13.5pF]
From Page 65 of [O19], Continuum Surelite Laser Manual (KD*P crystal):
'The combination of a polarizer, Pockels cell and 1/4 waveplate within the oscillator is known as a Q-switch. A Q-switch prevents lasing in the resonator until the laser gain reaches its peak and then opens the cavity to allow oscillation. This then produces ultra-fast, high peak power laser pulses. The Pockels cell has a longitudinal field KD*P crystal with a 15mm. clear aperture mounted at 43mm beam height. A voltage of ~3600V results in a quarter wave of rotation for photons at 1,064nm passing in either direction. A voltage of 0 volts results in no rotation. The thin film multilayer dielectric polarizer has an angle of incidence of 57°. In its standard orientation, the polarizer is highly transparent (>95%) to horizontally polarized light while being highly reflective (>99%) to vertically polarized light. The contrast/extinction ratio is >500:1.
CAVITY CLOSED
The beam propagating within the oscillator cavity makes a double pass through the Pockels cell and 1/4 waveplate. At 0 volts on the Pockels cell (PC) it adds no rotation while the 1/4 waveplate adds 45° with each pass, giving a total rotation of 90°. Thus the horizional beam that transmitted through the plate polarizer is rotated to vertical and is rejected by the polarizer and no oscillation occurs.
CAVITY OPEN
The beam propagating within the oscillator cavity makes a double pass through the Pockels cell and 1/4 waveplate. At 3600 volts on the PC it adds 45° rotation and the 1/4 waveplate adds 45° with each pass, giving a total rotation of 180°. Thus, the horizontal beam that transmitted through the plate polarizer is rotated to vertical and back to horizontal, so that it is transmitted by the polarizer allowing oscillation to occur.'
As NLOs, Pockels cells are made from several compounds and each has their strengths and weaknesses.
The Inrad datasheet for their PCB06 series BBO pockels cells [N6] highlights some of the disadvantages of other NLOs. Unfortunately I am stuck with whatever parts became available and it would not surprise me if they are not made of BBO.
b. EXPERIMENTAL
[O25], DIY techniques for passive Q-switches - RENUMBER Wnn & SAVE AS WEBSITE SCREENSHOT
c. MECHANICAL
Experimental mechanical shutter using an optical chopper to emulate one in this US Navy paper:
[O14] 'Performance of a Diode-Pumped Laser Repetitively Q-Switched with a Mechanical Shutter'
d. PASSIVE
Beckman & Whitley model 450 thin film passive Q-swt 48% for ruby
Beckman & Whitley model 455 thin film passive Q-swt 57% for ruby
[N8], Electronics magazine Oct 18 1965, Page 93: short article on Beckman & Whitley passive Q-switches of this type for a ruby laser.
12. WAVEPLATES / POLARISERS
HE 1/2 wave plate 1064nm 5mm square x 2mm HE but characteristics unknown
Quartz 1/2 wave plate 1064nm (pass 532nm) 25mm CVI QWPD-1064-2-532-1-10 (10J/cm²)
Quartz 1/2 wave plate 1064nm 0 order mounted Spectra Physics (Newport = 2J/cm²)
Quartz 1/4 wave plate 1064nm 0 order mounted Spectra Physics (Newport = 2J/cm²)
Quartz wave plate multi-order 12.5mm CVI QWPM-1064-05-2 (05=0.5 inch,2=half 10J/cm²)
Thin film Brewster plate polariser CVI TFP-1064-RW-28.6 14.3-3.2 (28x14x3mm thk 20J/cm²)
Motorised 532nm zero order half wave plate
Laser Polarisation is random, S, P or Circular rotation of the beam eg clock positions 12/3/6/9pm.
Waveplates rotate polarisation or convert light from linear to circular and vice versa. If linearly polarised light is incident upon a mirror the polarisation is rotated 180° to the incident beam.
a. Half wave plate to align 532nm to 266nm harmonic crystal
b. Quarter wave plates for laser resonators
13. PRISMS
Pellin broca
Coherent 213nm pellin broca prism New P/N 5567-001-PV
A pellin broca prism splits wavelengths, e.g. 532nm 1.26 degrees away from 1064nm
Used by the YAG 193nm paper [O12] to separate outputs to independent focus lenses. This has 4 sides. The beam enters the first side and is dispersed into its rainbow of wavelengths internally to the next surface, where total internal reflection (TIR) occurs and the separated wavelengths exit at the third surface. The angle between entry and exit for the design wavelength (e.g. 213nm) is 90°. I will use the pellin broca to separate the 694nm ruby from the Nd:YAG wavelengths. To measure separate wavelengths I will compare relative magnitude on spectrometer wrt measured raw 1064nm.
14. VISUALISERS
UV TO VIS CONVERTER
Metrolux K7 20x20x3mm, 110nm-350nm to 612nm peak
Product Type Wavelength Decay (10%) Emission Peak = Cohu 4815 Peak Val
K7 Fluorescence 110nm-350nm 3ms 612nm 0.75
15. WINDOWS
1064nm UV 37.5mm dia x 4.8mm thk Resonetics UVL-1.5-8000 (made for IBM)
1064nm/532nm/266nm FS 25.4mm dia x 6.4mm thk AR/AR
400-700nm BK7 25.3mm dia x 6.4mm thk AR/UC
694nm 25.4mm dia x 3.0mm thk AR/AR
UVFS 25.4mm dia x 6.5mm thk MG PW1-1025-UV
AR windows are required for pressurised target chamber.
Nd:YAG 1064nm-266nm in - use AR 1064nm/532nm/266nm or UVFS
Ruby 694nm out - use 694nm
Argon 488nm in - use AR 400-700nm
PCM401 200nm-900nm out - use UVFS
camera 400nm-1100nm out - use UVFS
Nd:YAG 193nm in - use UVFS
16. X, Y, Z MOUNTS
Diameters of optics I need to mount:
USE: Y=LHC, R=Ruby/Ti:S/THC laser, ? = maybe
? 4 x 1/100 532nm bmsplt 9.8mm dia x 2 thk 45 1% reflect
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? 1 x £1 ceramic pinhole 0.5" 12.5mm dia & 0.80mm hole dia
R 1 x Ti-S 700-800nm OC 12.5mm dia x 3/8" 95%
? 1 x multi-order HWP 12.5mm dia x ?? mm CVI QWPM-1064-05-2 (05=0.5 inch, 2=half 10J/cm²)
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R 1 x 694?? 40J/cm²? mirr 22.0mm dia x 3.15mm thk mirror in box marked HENE
R 1 x 694nm + 632nm mirr 22.0mm dia x 3.15mm thk mirror to use as ruby HR
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R 1 x 700nm HE cavity mirr 25.0mm dia x 6.35mm thk Coherent folding mirror 690nm-835nm
Y 1 x 488nm argon mirr 25.0mm dia x ?? mm thk 0.1% tx @ 488nm limits 450nm-500nm
Y 1 x 1064/T532nm HWP 25.0mm dia x ?? mm thk CVI QWPD-1064-2-532-1-10 (10J/cm²)
Y 1 x 1064nm ±3nm 1064 BP12 25.0mm dia x 3.00mm thk Tx>95% sputtered 5J/cm²: block UV-1200nm flsh
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Y 1 x 1064nm lens 25.4mm dia x ?? mm thk PLCX 76.6mm FL (tested: >315nm only)
Y 1 x 1064nm lens 25.4mm dia x ?? mm thk PLCX mebe3d 50-55mmFL in square holder
Y 1 x uncoated lens 25.4mm dia x ?? mm thk PLCX UVGSFS (175nm - 2.0µm) UV focus
Y 1 x 694nm 50% AR/AR OC 25.4mm dia x 6.35mm thk ROC1.00m Spectrosil-B
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? 2 x 400-1064nm 50/50 bmsplt ?? mm (to attenuate beam to measure/compare loss through SHG NLO)
Y 2 x 532 1064 266nm bmsplt 25.4mm dia x 6.35mm thk 45 T532nm & 1064nm/R266nm (266nm to target)
Y 1 x 532 1064 355nm bmsplt 25.4mm dia x 6.35mm thk 45 T532nm & 1064nm/R355nm
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? 1 x 1064nm HE 45AOI mirr 30.0mm dia x 4.00mm thk flat 40W Chinese
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? 2 x 193nm ±18nm 1.5" mirr 37.5mm dia x 5.00mm thk 45 AOI 175-210nm ARC 193-FR45-1.5D-FL
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Y 1 x 1064nm ±114nm 2" mirr 50.0mm dia x 3/8" thk 45 AOI 950-1175nm CVI Y1-2037-45-UNP
N 1 x T<=633nm/R1064nm 45AOI 50.0mm dia x 6.40mm thk 10J/cm² CVI SWP-45-RS1064-TP633-PW-2025-C
Summary of non 25.4mm or 25mm dia optics I need mounts for:
-----------------------------------------------------------
1 x Ti-S 700-800nm OC 12.5mm dia x 3/8" thk 95%
1 x 694?? 40J?? mirr 22.0mm dia x 3.15mm thk mirror in box marked HENE
1 x 694nm + 632nm mirr 22.0mm dia x 3.15mm thk mirror to use as ruby HR
1 x 1064nm ±114nm mirr 50.0mm dia x 0.375" thk 45 AOI 950-1175nm CVI Y1-2037-45-UNP
These are all mirrors, so not best in self-centre holders.
Instead they need to be in adjustable mirror holders to be set to EXACTLY 0 or 45 AOI.
Should be able to mount them all in or on top of Coherent's existing mounts?
OPTICAL HARDWARE & MOUNTS
1 x Optical breadboard 2' x 4'
1 x DIY stepper motor controlled rotary stage for target
1 x Oriel 18006 0.5in Motor Mike & 18018 controller - use with Coherent linear stage for focus
6 x Newport LP-1-XYZ 1" adjustable lens mounts
3 x Thorlabs MB175/M M6 magnetic mounts
1 x Newport VLH-3 adjustable lens mount 0.600" to 3.600"
1 x OWIS motorised rotary stage with 0 order 512nm HWP (for HG)
1 x OWIS motorised rotary stage (for HG)
1 x Oriel precision rotary stage
1 x Edmund Optics rotary stage EDM-39159A, 120mm Square x 26mm
1 x Melles Griot 3-axis rotate tip tilt stage with clamp for square edge optics (for tophat)
9 x Thorlabs job lot of vertical stages & posts & XY mount & rotary mount
1 x Photon Control vertical rotary mirror mount on Thorlabs mount (for birefringent filter)
1 x HUGE lot of 1"? optics & mounts from Quantel 1GW Nd:YAG (various)
6 x Continuum 1" optics in top adjust mounts
4 x Newport 5153 0.5" silver mirrors in Newport 9775 top adj mounts (main mirrors)
2 x Passat square optic mounts with 2 mirror adjustments (HWP, UV-VIS converter)
17. OPTICAL BREADBOARD
At the start of the LHC project I decided I would employ professional equipment and optical hardware.
Optical mounts are designed to be bolted to a breadboard usually consisting of a monocoque of a metal sheet on a honeycomb or similar rigid internal support structure. The top metal sheet has a precision matrix of tapped holes into which the hardware is bolted:
https://www.baselabtools.com/Optical-Breadboard_c_87.html
It was clear I would need one of these and as I began to collect the hardware, I concluded the ideal size for the LHC project would be one measuring 4 feet x 2 feet that would allow room for experimentation as well as a full final layout, but several obstacles appeared:
The UK surplus market has next to no optical hardware so most of mine came from the USA which employs the imperial measurement standard, and holes are usually tapped for 1/4-20 screws with 1 inch spacing.
Optical breadboards are very expensive, even used on eBay, and due to their considerable weight, are prohibitively expensive to ship to the UK.
Imperial fasteners are rare in the UK which instead complies with the European metric standard, and UK-made optical breadboards are metric, usually with M6 tapped holes on either 1" or 25mm spacing.
There were one or two specialist metric items I did buy, and I had to find a way to accommodate both standards onto the breadboard.
DIY 2' x 4' BREADBOARD
The only solution was to make my own. As most of my hardware was imperial I decided I would use imperial spacing at a reduced 0.5" so if necessary I could construct adaptor boards to accommodate metric hardware, and 5mm holes that could be tapped to M6 by default, and 1/4-20 if essential.
It was beyond my abilities to drill a precision hole matrix, but a local metal fabricator came to the rescue and made the sheet for me for £130 (~$200). I discovered they actually punched the holes rather than drilled them, but the result was the same. .
Funds limited the maximum sheet thickness I could afford and I settled for 3mm which I reasoned tapped threads should just hold. If this isn't the case, I'll add thicker plastic sheeting below and drill it through the metal sheet before tapping both.
The sheet is screwed to a wooden frame I made myself, with the screws on the smaller 0.5" matrix which should stop them interfering with the optical hardware. However if this becomes and issue I may replace some of them with super magnets in the same way the MK367 heatsink is secured to the Prototype tray.
NEWPORT SG 600 x 900 BREADBOARD
In 2022 I found a Newport SG (Scientific Grade) 600mm x 900mm x 59mm M6 metric optical breadboard in great condition for £300 cash not far from my home. At the time I was looking for a smaller one to run experiments on but I recognised I would be very unlikely to find another one this size at a better price. 600mm x 900mm is roughly 2' x 3' and together with the Quanta Ray quad HG assembly I think I have a good chance of getting the entire system on it. I now no longer have to worry about improving my DIY version which is also nowhere near its ±0.1mm flatness: https://www.newport.com/p/M-SG-23-2-ML
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