Improvements of performance of high-power multimode laser diodes and arrays achieved by use of Volume Bragg grating~(™) technology

摘要

High-power laser diodes (or HPLDs) and laser diode arrays with output power extending into kilowatt range have been accepted by the industry over the years as an enabling technology for a variety of applications, such as pumping of the solid-state lasers, medical treatment, Raman spectroscopy etc. At the same time, broad spectral line width, large thermal drift of the wavelength and, particularly, poor spatial beam quality of the broad-area laser diodes are recognized as common deficiencies. Recently the technology of the volume Bragg gratings~™ (VBG™) has been applied to the problem of improving spectral characteristics of the high-power broad-area laser emitters and arrays that demonstrated a very simple and robust way to stabilize the emission wavelength and simultaneously narrow the line width of single-emitter HPLDs, laser diode bars and even stacks. The VBG™ technology achieves passive wavelength stabilization (drift ～ 0.01 nm/K) and line narrowing (typical line width ～ 0.2 - 0.4 nm FWHM) without changing the form factor of the packaged laser diodes and laser diode arrays. The current paper describes the recent advances in applying the VBG™ technology to improving the spectral characteristics of the HPLDs and laser diode bars and also the results on improving the spatial brightness of these devices.