Phase-Shifted, Chirped Volume Bragg Grating (VBG)

Abstract

Researchers at the University of Central Florida have developed techniques for fabricating a new hybrid photonic element. Part of a novel class of hybrid grating, the UCF Phase-Shifted, Longitudinally Chirped Volume Bragg Grating (LCVBG) can be used to support tunable solid-state lasers with multiwavelength emission. The technology is capable of encoding phase information into both (1) the relative shift between local Bragg elements, and (2) the Bragg-period variation across the grating volume.

In the passive form, the phase-shifted, chirped VBG is a spectral beam shaper, wavelength-tunable across the transverse plane of its facet. The element is further doubled as a distributed feedback laser (DFB) when recorded into the optically active volume of doped photo-thermo-refractive (PTR) glass. The invention may also be used to create THz or GHz emitters for various applications.

Technical Details

In one application of the UCF invention, the example figure shows a phase-shifted, chirped VBG with a single notch axis, recorded in the optically active medium of doped PTR glass. In essence, it is a transversely chirped, distributed feedback laser (TCDFB). Packaged in a compact, monolithic volume of PTR glass, the grating element features an extended degree of resistance to high average- or peak-power laser radiation, mechanical shocks, and elevated temperatures.

End-pumped from one side by a laser diode with the emission wavelength tuned to around 981 nm, the active emitter matches the peak absorption of doped PTR glass. The monolithic source emits a pair of continuous-wave, single axial-mode laser beams near 1066 nm, from the element’s front and back facets. Analyzed by a scanning Fabry-Perot with 10 GHz of free spectral range, the axial-mode content at a diffracted output revealed the single-mode characteristic of coherent light being generated.

The versatile TCDFB element is a continuous collection of DFB sub-emitters, linearly distributed along the device’s end-facets. Due to the lack of cavity resonances, the change in emission wavelength is theorized to be continuous, mode-hop free over the entire tunable bandwidth—without the added complexity of phase-locking loops found in commercial devices. The rate of spectral tuning, though a fixed parameter, is adjustable during recording, as defined by the relative angle between the notch and chirp axes of the embedded grating.

Partnering Opportunity

The research team is looking for partners to develop the technology further for commercialization.

Stage of Development

Prototype available.

Benefit

Market Application