2 μm semiconductor disk laser with a heterodyne linewidth below 10 kHz

Abstract

We demonstrate a 2 μm semiconductor disk laser emitting in a single longitudinal mode with a linewidth in the <10 kHz range. A heterodyne detection scheme was used for precise linewidth measurements. In these experiments, the output beams of two identical laser cavities were superposed in order to generate a beat note signal on a photodiode. In the absence of active frequency stabilization, a linewidth of 45 kHz was measured at an output power of 100 mW. When using a frequency stabilization consisting of a feedback loop with a Fabry-Perot interferometer as wavelength reference, the linewidth could be further reduced to 9 kHz.

Semiconductor disk laser at 2.05 μm wavelength with &lt;100 kHz linewidth at 1 W output power

“…9 The narrowest linewidth of <10 kHz reported so far for this wavelength range was achieved at 2.0 lm with an output power of 100 mW. 10 Building on the latter work, we demonstrate in the present paper that 2.0 lm-emitting SDLs are capable of laser emission with a linewidth below 100 kHz at an output power above 1 W, thus surpassing even established MIR kHzlinewidth laser sources, such as solid state lasers, 11 by more than a factor of 15 with respect to output power.…”

“…This resonator was integrated in a mechanically stable, rugged, and sealed module housing, machined from a solid block of aluminium. 10 The cavity (length: 163 mm) was operated close to its stability limit, so that the calculated diameter of the fundamental elliptic Gaussian mode on the chip amounted to 510 lm (570 lm) in the tangential (sagittal) plane. The 980-nm pump light was focussed on the chip to from aside under an ankle of 30 , resulting in an elliptic spot with a half-axis ratio of 1:1.15 and a size clearly smaller than the cavity mode size.…”

Optically pumped VECSELs: review of technology and progress

“…Nevertheless, such measurements with delay lines shorter than the laser coherence length have been used for determining a lower limit for the coherence length [275][276][277], which can then provide a rough estimate for the upper limit of the laser linewidth [278]. In practice, the VECSEL linewidth is typically determined using heterodyne measurements with two similar lasers [266,279,280] or from the frequency noise spectral density via calculation [227,259,281,282]. In any case, the linewidth increases with the sampling time as more noise sources are taken into account [266,268,280,283].…”

Generation of new spatial and temporal coherent states using VECSEL technology: VORTEX, high order Laguerre-Gauss mode, continuum source

“…Since years, the VeCSEL concept is pointed out as a technology of choice for beyond-state-of-the-art laser light sources, 1, 2 demonstrating wavelength flexibility, [3][4][5][6][7][8] high power, [8][9][10][11] high spatial, temporal and polarization coherence, 7, 10 CW or fs ultra-short pulsed operation, [12][13][14][15][16] compactness and functionalities. [17][18][19] The targeted coherent state is typically a common circular low divergence fundamental gaussian TEM00 mode, linearly polarized state, single frequency state or modelocked comb.…”

“…Such high-Q laser cavity exibits a class-A dynamics with low intensity noise at shot noise level in MHz-RF range, as well as a quantum limit optical frequency noise at the Hz level. 11,20,21 Integration and packaging of such high performances sources is in progress (by Coherent, Innoptics, 22 Fraunhofer ILT...).…”