Volume Holographic Gratings (VHGs) – Ultra-narrowband, High Performance Filters with Unlimited Lifetime
Ondax VHGs, also commonly referred to as Volume Bragg Gratings (VBGs), are bulk “solid-state” diffractive Holographic Optical Elements (HOEs, or filters), formulated from a proprietary solid, transparent photo-thermal-refractive (PTR) glass substrate. Unlike thin films or gels, VHGs deliver ultra-stable, degradation-free performance for the lifetime of the filter. The entire glass substrate is “recorded” with a phase volume diffraction grating using a UV laser source, then thermally treated at high temperatures (>400⁰C) to effect a permanent refractive index change in the bulk material.Capable of very tight wavelength, efficiency, bandwidth, and diffraction angle control, Ondax VHGs can be precisely and reproducibly engineered to demanding spectral and temporal specifications for a wide variety of applications. Available in either reflective, transmissive, or chirped Bragg grating configurations, Ondax VHGs can be manufactured with specified wavelengths ranging from 375nm to 2.5μm, efficiencies from 5% to >99%, bandwidths from 0.03nm to 1nm, and sizes up to 30mmx40mm, allowing customization to match nearly any application requirement. They are also capable of sustained operation at highly elevated temperatures (>200 deg. C), have extremely high laser damage thresholds, and can be confidently used in space or vacuum environments.The most common applications for VHGs include:
- Laser diode wavelength stabilization (for solid state laser pumping and analytical instrumentation)
- Ultra-narrowband spectral filtering (for low-frequency/THz-Raman Spectroscopy)
- Pulse stretching and compression (for chirped pulse amplification)
- Wavelength Beam Combining (for high-power lasers and wavelength multiplexing)
Reproducible Manufacturing and Performance – Guaranteed.
All Ondax VHGs are manufactured using automated wafer-level manufacturing processes and patented1 high-resolution, metrology systems that simultaneously measure all 4 specified optical parameters – wavelength, bandwidth, diffraction efficiency slant angle –at every point on a 140 micron-pitch grid (or “pixel”). This proprietary and exclusive high-resolution process ensures that we can guarantee every specification is met across every filter regardless of size, delivering exceptional process control and reproducibility. Every individual filter is measured and data provided with a Certificate of Conformance documenting # of test points, wavelength, efficiency, bandwidth, and slant angle for each filter.
1. US Patents 7,359,046, 8,049,885, and 8,139,212
For more information on VHG technology and performance parameters, see our article “Filters to Bragg About” or visit the PowerLocker product page and click on the Downloads tab at the bottom of the page.