High power single–frequency continuously–tunable compact extended–cavity semiconductor laser

Abstract

We demonstrate high power high efficiency (0:3 W) low noise single frequency operation of a compact extended-cavity surface-emitting-semiconductor-laser exhibiting a continuous tunability over 0:84 THz with high beam quality. We took advantage of thermal lens-based stability to develop a short (< 3 mm) plano-plano external cavity without any intracavity filter. The structure is optically pumped by a 1 W commercial 830 nm multimode diode laser. No heat management was required. We measured a low divergence circular TEM(00) beam at the diffraction limit (M(2) < 1:05) with a linear light polarization (> 37 dB). The side mode suppression ratio is 60 dB. The free running laser linewidth is 850 kHz limited by pump induced thermal fluctuations. Thanks to this high-Q external cavity approach, the frequency noise is low and the dynamics is in the relaxation-oscillation-free regime, exhibiting a low intensity noise, with a cutoff frequency approximately 250 MHz above which the shot noise level is reached. We show that pump properties define the cavity design and laser coherence.

Experimental study of the delayed threshold phenomenon in a class-A VECSEL

“…have been shown to exhibit very long cold cavity decay times together with remarkably low noise levels [16,17,18].…”

Observation of noise phase locking in a single-frequency VECSEL

“…The laser is optically pumped at 808 nm. The gain is broad (∼ 6 THz bandwidth) [7]. In order to obtain single-frequency operation, a glassétalon (200 µm thick) is inserted inside the cavity.…”

VECSEL Semiconductor Lasers: A Path to High‐Power, Quality Beam and UV to IR Wavelength by Design

“…In this case, laser transverse mode is stabilized by gain aperturing with strong optical loss outside the pumped spot on the chip. Another compact version of the two-mirror VECSEL cavity is the microchip laser configuration [69][70][71]140], where a short plane-plane laser cavity is transverse mode stabilized by a thermal lens formed in the gain medium due to temperature gradients within the pump spot. Here, intracavity diamond heat spreader was used, with its planar outer surface coated with high-reflectivity output coupling mirror [70]; on-chip mirror is the second mirror of the cavity.…”

“…The ways to achieve this will include using broadband gain semiconductor materials, such as quantum dots (Chapter 5); broadband OPS chip gain structures with quantum well, or dot, layers displaced somewhat from their periodic RPG positions [18,130]; multiple, nonidentical gain chips in the cavity [51]; and, also important, low-loss tunable filters. Single-frequency tuning of VECSELs [55,140,164] is also important and will see further development for some applications, such as laser sources for atomic clocks [120,146] and spectroscopy [106].…”

“…A number of studies have explored properties of VECSELs in their single-mode operating regime, such as laser linewidth, which can be very narrow in the kilohertz range [55,104,106,119], and relative intensity noise (RIN) and its spectrum [56,140]. Such single-mode operation has been achieved both with intracavity filters [55,56,59,221], such as etalons, birefringent filters, and volume Bragg gratings, or alternatively free running without intracavity filters [106,140]. Single-mode operation has been demonstrated both for the fundamental and intracavity frequency-doubled VECSELs [222].…”