Beam Attenuators and Optics

ATP-K Variable Attenuator

The ATP-K attenuates your laser without ghost reflections or fringes and has a knob-operated variable wedge attenuator of OD 1.7 - 4.6, and comes with a fixed gray-glass attenuator with OD 2.8. The ATP-K is also designed to be used with Photon-supplied high power attenuators and beam splitters. High-power attenuators attach directly to the ATP-K via a C-mount. The ATP-K has simple reproducible attenuation settings.

Figure 1 shows the safe average power for negligible beam distortion from thermal lensing. Absorptive filters, such as used in the ATP-K, have an upper power limit of approximately 100mW per mm diameter beam diameter. For pulsed beams, Figure 2 shows the damage threshold for energy where breakage of the glass wedge may occur. This is approximately 5J per mm beam diameter. For lasers with power or energy levels above this the first stage of attenuation will need to come from our line of high power reflective attenuators.

High-Power Attenuators

Our high-power laser mirror attenuator transmits <1%, and comes in a C-Mount threaded adapter ring. It is also AR coated for either straight on or 45° orientation.

Note that if more than one reflective attenuator is required to reduce the beam power, one of them must be oriented 45° to the beam. Unlike absorptive attenuators, reflectors cannot be stacked, because they will form a laser cavity.

Available standard configurations

• HP-266‹Use for 266 ±50nm
• HP-355‹Use for 350 ±50nm
• HP-450‹Use for 450 ±50nm
• HP-600‹Use for 500-700nm
• HP-800‹Use for 700-900nm
• HP-1064‹Use for 1000-1100nm
• Other wavelengths available upon request

Filter Wheels and Sets

Single and double filter wheels are designed to hold six 25mm filters per wheel. Filters are available separately or as a set of 13 neutral density filters.

Front Surface Attenuators

Photon offers wavelength-independent fused silica front surface reflectors for attenuation of the highest beam powers and energies, right angle prisms. The fused silica prism, used at 45° incidence, reflects 4% of the incident beam into the camera. The prism is mounted to a C-mount fixture for attachment to the camera. The internally reflected secondary beams scatter away from the 4% beam.

Interferometer-quality quartz plate is mounted in kinematic mirror mount with post and sleeve to provide 4% front-surface reflection for attenuation and fine adjustable beam steering. Using 2 plates at 45-degree incidence, orthogonal to one another, will preserve beam polarization state. If used singly, the angle of incidence should be kept low to preserve polarization of test beam.

It is mounted on the optical bench and may be used singly or for multiple reflections for a cascading attenuation effect. Front surface reflections are polarization dependent, and thus for polarized beams these should be used in pairs to preserve the polarization state of the test beam. These plates also allow 96% of the beam to pass directly through, and therefore it is important for safety that there be proper beam dumps arrayed to catch the beam, particularly on the first stages of attenuation.

Prism Front-Surface Beam Attenuator

The Prism Front-Surface Beam Attenuator (PFSA) is a C-mount fixture housing a UV-Grade Fused Silica right angle prism, used for sampling the front surface reflection for high power/energy beam profiling applications. Surface Quality is 20-10 and Surface Accuracy is λ/10. It is intended for use in conjunction with the ATP-K attenuator and BeamPro cameras for measurement of high power/energy lasers. Reflection at nominal incidence of 45° is polarization and wavelength dependent, with 532nm s-polarization reflected at 8.27%, and p-polarization at 0.68%. Use of 2 units configured orthogonally results in polarization independent reflection of 0.057% at 532nm. Other filters and attenuators can be attached using the C-mount female threads at the input end.

Flip-Mount Filter

The Flip-Mount Filter is a C-mount fixture with a nominal OD2.8 filter mounted in a hinged adaptor that allows the filter to be easily flipped in or out of the beam path. The nominal optical density extends from 400-1500nm and the useful range extends beyond 2500nm. Surface Quality is 20-10 and Surface Accuracy is Θ/10. The Flip-Mount Filter is intended for use with the ATP-K attenuator for BeamPro cameras. Other filters and attenuators can be attached using the C-mount female threads at the input end.

Right-Angle Prism

The use of a right-angle prism (below, right) to sample the incident beam guarantees that any scattered secondary beams do not interfere with measurement, as shown in the sketch. A beam dump can be placed at the open end of the unit to intercept the main transmitted beam.

ATP-K Specifications
Optical/Sensor/Detector
Maximum Power/Energy Handling:	100 mW/mm beam diameter 100 mJ total avg. energy Damage threshold: 5J
Note: Very powerful laser sources may require additional attenuation prior to the beam's exposure to Model ATP-K. This can be achieved using front surface reflections from wedged quartz plates, and/or transmission through laser grade mirrors
Wavelength Range:	360-2500+ nm; near flat response out to1500nm
Attenuation Range:	Variable filters: OD = 1.7 to 4.6
Standard Low Power Removable Attenuation	OD 2.8 Glass Neutral Density Filter
Note: OD (optical density) = log (1/T) or T=10 (-OD) where T is the fraction of light transmitted. For example, an OD of 5 transmits 0.00001 or 0.001%.
Clear Aperture:	15mm diameter
Dimensions in mm:	94 W X 28 H X 43 D
Thickness Tolerance:	±0.25mm
Mounting:	C-mount
Base Mount:	1/4-20

Specifications subject to change without notice

High-Power Attenuator, Prism Front-Surface Beam Sampler, and Flip-Mount Filter Specifications are all available upon request.

• FireWire BeamPro CCD camera-based beam profiler
• USBeamPro CMOS camera-based beam profiler
• Application Note: Attenuation-Induced Error due to Thermal Lensing in Beam Measurement