Highly Coherent, Widely Tunable 2-3µm GaSb VeCSELs

, by Arnaud Garnache, Jean-Philippe PEREZ, Laurent Cerutti, Mikhael Myara

Particularities for the design of Mid-IR VeCSELs

The design of Mid-Infrared VeCSELs implies some difficulties :

  • Pump lasers are usually short wavelength lasers, so the photon energies due to pump emission and laser emission are very different, leading to increased heating of the laser structure,
  • Owing to their gap, the typical semiconductor material for mid-IR light generation, which thermal conductivity is smaller than the one of GaAs,
  • Non-radiative recombinations, such as Auger effects, increase with the wavelength.

For these reasons, the membrane technology with high thermal conductivity host substrate is a key point for the development of high performance, continuous wave high power mid-IR VeCSELs. This technology is under improvement at IES.

We specifically developed VeCSELs for gas analysis for 2.3µm for CH4 (methan) spectroscopy and 2.7µm for isotopic ratio measurements.

Main properties

All the properties of GaSb VeCSELs are similar to the ones of GaAs, except the optical power : the optical beam is still a low divergence, highly coherent beam. Here are the optical power properties of 2.3µm and 2.7µm VeCSELs on GaSb host substrate (thus without specific thermal management).

These values were obtained for high coherence TEM00 emission (M2<1.2), single frequency with high SMSR (>45 dB) and highly polarized electrical field (>35 dB).

An very important property for the targeted spectroscopic applications is the continuous tunability. Our VeCSELs exhibit broadband continuous tunability, up to THz without mode-hopping. Here is an experimental demonstration with a 2.3 µm VeCSEL compared to Hitran data.