High average output power from a backside-cooled 2-µm InGaSb VECSEL with full gain characterization

Abstract

We compare the gain and continuous wave lasing properties of two InGaSb-based vertical external cavity surface emitting lasers (InGaSb VECSEL) with different heat management approaches operating at a center wavelength of around 2 μ m . To date, intracavity heatspreaders have been required for good average output power, which have many trade-offs, especially for passive modelocking. Here we demonstrate a record high average output power of 810 mW without an intracavity heatspreader using a backside-cooled non-resonant VECSEL chip optimized for modelocking. In addition, we introduce and demonstrate an optical characterization for a wavelength range of 1.9 to 3 μ m to precisely measure wavelength-dependent gain saturation and spectral gain. Gain characteristics are measured as a function of wavelength, fluence, pump power and temperature. Small signal gain of more than 5%, small saturation fluences and broad gain bandwidths of more than 90 nm are demonstrated. In comparison to a commercial VECSEL chip with an intracavity heatspreader, we have obtained similar average output power even though our VECSEL chip is designed for antiresonance.

2-μm 1.5-W Optically Pumped Semiconductor Membrane Laser

“…A standard 2-µm VECSEL structure [17] in comparison, has a total thickness of 6.7 µm. The active region consists of 4 sets of 3 In 0.27 Ga 0.73 Sb quantum wells (4 × 3 QWs), where each QW has a thickness of 8 nm.…”

“…After bonding, the GaSb substrate is removed by lapping down to 20-40 µm followed by wet-etching the remaining substrate with a solution mixture of 33 % CrO 3 and 50 % hydrofluoric acid, diluted in water 1 : 5 [17]. The InAs 0.91 Sb 0.09 etch stop is then removed with a solution of citric acid and hydrogen peroxide yielding the finished MECSEL chip on a single SiC heatspreader.…”

“…GaSb-based VECSELs have been modelocked [7] and high-quality InGaSb SESAMs [15] enabled shorter pulses and higher output power [16]. The thermal resistance for cw 2-µm VECSELs [17] could be reduced with a hybrid metal-semiconductor Bragg reflector [18]. More recently a GaSb-based MIXSEL has been demonstrated in single-and dual-comb operation [19].…”

324-fs Pulses From a SESAM Modelocked Backside-Cooled 2-μm VECSEL

“…The saturation fluence is especially important for the quasi-soliton pulse shaping mechanism in modelocked VECSELs [11]. A detailed description of the structure design, the wafer removal process, and chip characterization is given in [12]. The In0.27Ga0.73Sb QW SESAM is also MBE grown and directly soldered (GaSb wafer side) to a copper heat sink.…”

Extending hybrid integrated diode lasers to multi-frequency oscillation

“…Also for the proper timing of single-photon light sources by time multiplexing [51] low repetition rates are needed. Of course, low repetition rate lasers have been available for long, but these are exclusively bulk lasers requiring optical pumping, specifically, rareearth doped solid state lasers, fiber lasers, and optically pumped semiconductor lasers [163]. These are less suitable for high functionality, complex optical systems.…”