The digital laser

TL;DR

This paper introduces the digital laser, a novel system using a programmable holographic mirror within the laser cavity to dynamically control and switch between various laser modes without physical modifications.

Contribution

It presents the first digital laser that employs an electrically addressed phase-only spatial light modulator as an intra-cavity holographic mirror for on-demand mode control.

Findings

Successful digital control of laser modes demonstrated

Ability to switch between multiple spatial modes easily

Maintains laser operation with standard resonator setup

Abstract

It is well-known how to control the spatial output from a laser, with most solutions to date involving customised intra-cavity elements in the form of apertures, diffractive optics and free-form mirrors. These optical elements require considerable design and fabrication effort and suffer from the further disadvantage of being immutably connected to the selection of a particular spatial mode. Consequently, most laser systems are designed for the ubiquitous Gaussian mode, whereas it is clear that there are many instances when a customised mode would be preferable. We overcome these limitations with the first digital laser, comprising an electrically addressed reflective phase-only spatial light modulator as an intra-cavity holographic mirror. The phase and amplitude of the holographic mirror may be controlled as simply as writing a new gray-scale image (computer generated hologram) to the device: on-demand laser modes. We show that we can digitally control the laser modes with ease, albeit with higher round-trip losses and thus requiring higher gain, and demonstrate the versatility of the technique by switching between several spatial modes in an otherwise standard solid-state laser resonator.