Diffractive optical elements for high gain lasers with arbitrary output beam profiles

Abstract

We introduce a previously unreported laser cavity configuration, using a diffractive optical element (DOE) in place of the output coupler. Such a configuration allows the DOE to work both in reflection, as a mode shaping element, and in transmission as a beam shaper. Employing dual wavelength DOE optimization techniques and phase delays greater than 2pi, allows the two functions to be designed independently. Thus, an arbitrary output beam profile can be combined with a mode shape which maximizes energy extraction from the gain medium. Devices are designed and their performance modeled for a 1m cavity with 5mm diameter mirrors and a wavelength of 632.8nm. An element with 32 quantization levels and a maximum phase delay of 8pi in transmission produces high quality results.

A digital laser for on-demand laser modes

“…However, there are advantages to rather shaping the light inside the laser cavity (intra-cavity laser beam shaping) and this has been a subject of interest for a number of years [2][3][4] , with several design techniques available [5][6][7][8][9][10] , some of which have successfully been implemented, for example, using phase-only [11][12][13][14] , amplitudeonly 15,16 and phase-amplitude combination 17 optical elements for spatial mode selection. All of these techniques require custom optics and in some cases (for example, Bourderionnet.…”

Diffractive and micro-optics for wavefront manipulation

“…A schematic of the processing chain is shown in Figure 5. The DOE phase profile (which consists of a power-of-two number of phase levels) is converted into a binary amplitude photolithographic mask set -each mask level contains opaque and clear areas corresponding to non-etched and etched areas for that power-of-two level [11]. Suitable alignment structures, which have been designed to give better than 1μm alignment accuracy, are placed around the DOE structures to allow subsequent mask levels to be placed.…”

The digital laser: on-demand laser modes with the click of a button

“…Controlling transverse modes in a laser cavity is a difficult task experimentally, usually employing custom optical elements [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] in the form of diffractive and/or aspheric optics, adaptive mirrors or graded phase mirrors, or specialized apertures. Good beam quality associated with lower-order modes is a fundamental requirement for most laser applications.…”