Reflecting Volume Bragg Gratings

Wavelength 350-2700 nm; Bandwidth 0.02-20 nm; Diffraction Efficiency 3-99.7%; Thickness 0.50-20 mm; Aperture Up to 10x10-50x50 mm

OptiGrate’s reflecting volume Bragg gratings (RBGs) are diffractive optical elements operating in reflecting geometry when a diffracted beam crosses the grating surface frontally oriented to an incident beam. One of the particular cases of this geometry is the retro-reflection of an incident beam. Several products based on RBG elements with different reflectivity are available:

OptiGrate’s BragGrate™ Mirror is a reflecting volume Bragg grating recorded in a bulk of photosensitive silicate glass, suitable for laser mode selection and diode laser wavelength locking with a reflectivity range from 5% to 99% for spectral and thermal management of lasers. Incorporated in a laser resonator, a BragGrate™ Mirror enables the laser line spectral narrowing and thermal stabilization and can withstand high optical energy up to 5 J/cm². The laser modal structure is controlled by the longitudinal mode selection with the bandwidth down to 20 pm and the customized central wavelengths with an accuracy of 0.1 nm to 0.5 nm. BragGrate™ Mirrors have record low absorption and allow thermal laser wavelength shift reduction to 5 pm/K @532 nm.

BragGrate™ Notch Filter is a reflecting volume Bragg grating with very high diffraction efficiency, typically in a range of 90% to 99.9%, recorded in a bulk of photosensitive silicate glass. It serves as a ultra-narrow band-stop filter reflecting one narrow line (as narrow as 5 cm^-1) out of the transmitted laser beam, while all other wavelength pass unaffected with up to 95% total transmission. These volume Bragg gratings enable simultaneous measurements of Stokes and Anti-Stokes Raman bands down to 5 cm^-1 with a single-stage spectrometer. Our notch filters can withhold temperatures of up to +400°C and are fully environmentally stable with a practically unlimited lifetime. Central wavelengths of the filters can be angle-tuned by several nanometers without reduction of the filter optical density.

BragGrate™ Combiner is a high reflectivity (90-99%) volume Bragg grating (or sets of gratings) that is used for spectral beam combining (SBC). This element enables combining of laser radiation from multiple sources with offset wavelengths into a single, nearly diffraction-limited beam with increased brightness. SBC by means of our BragGrate™ Combiner is a simple and robust technique for combining high-power laser radiation with a record spectral brightness. Excellent mechanical properties and a refractive index that is independent of temperature enables the combiners to withstand high-power laser radiation, thus making the components the ideal element for high-powered SBC.

BragGrate™ Bandpass Filter is a reflecting volume Bragg grating (RBG) recorded in a bulk of photosensitive silicate glass. These filters are used to clean up laser spectral noise with a bandwidth as narrow as 50 pm in visible and near IR regions. In Raman spectroscopy applications, combining these Filters with matching BragGrate™ Notch Filters enables Raman shift measurements down to 5 cm^-1 from the laser line. The widely used BragGrate™ bandpass filters have superior environmental stability and can handle high power optical radiation and high operations temperatures.

Imperfections in laser optics and variations in laser gain medium cause side fringes and spatially varying intensity. Our BragGrate™ Spatial Filter is designed to “clean up” laser beams from these deficiencies. BragGrate™ Spatial Filters provide a simple, compact, and cost-effective solution for laser beam spatial filtering. They are based on reflecting volume Bragg gratings with a narrow acceptance angle that enables filtering of laser beams with a single element, thus replacing pinhole assemblies in case of narrow line laser sources. In addition to spatial filtering, BragGrate™ Spatial Filters provide ultra-narrow-line spectral filtering, can be used for high-power/high-energy applications, have superior environmental stability, and can handle high-power optical radiation and high operations temperatures.

Key Features:

• High-power Operations: >1 kW, Up to 10 kW
• High-energy Operations: Up to 5 J/cm²
• Superior Environmental Stability, No Degradation Over Lifetime
• No Polarization Dependence

Key Features BragGrate™ Mirror:

• Low to No Power Penalty
• Narrowing of Laser Line Down to 20 pm With Superior Thermal Stability
• Unique Solutions to Achieve SFM Oscillations
• Near-diffraction-limited Beam Quality

Key Features BragGrate™ Notch Filter:

• Ultra-narrow Rejection Bandwidth
• Measurements of Both Stokes and Anti-Stokes Modes

Key Features BragGrate™ Combiner:

• High Spectral Selectivity
• Near-diffraction-limited Beam Quality

Key Features BragGrate™ Bandpass Filter:

• High Spectral Selectivity
• Near-diffraction-limited Beam Quality

Key Features BragGrate™ Spatial Filter:

• Spatial Filtering Without Refocusing and Pinhole Assembly
• Highly Cost-effective and Small Footprint
• Easy Alignment by Angle-tuning in Standard Kinematic Mount
• Simultaneous Spatial and Spectral Filtering (<5 cm^-1 to Laser Line)
• Supports Operation at Temperatures up to +400°C

Applications: Longitudinal and Transverse Mode Selection in Laser Resonators; Solid-state Lasers; High-power Diode Lasers; MM and SM Diode Lasers for Spectroscopy; Fiber Lasers; Laser Radars; LIDARS; Ultra-low Frequency Raman Spectroscopy; Raman Imaging; Thomson Scattering; High-power Spectral Beam Combining; Filtering of Spatial Noise in Laser Beams; Ultra-narrow Linewidth Spectral Filtering of Laser Beams; ASE Filters for Diode Laser Sources; Wavelength-tunable Spatial and Spectral Filters