High-power tunable low-noise coherent source at 106 μm based on a surface-emitting semiconductor laser

Abstract

Exploiting III-V semiconductor technologies, vertical external-cavity surface-emitting laser (VECSEL) technology has been identified for years as a good candidate to develop lasers with high power, large coherence, and broad tunability. Combined with fiber amplification technology, tunable single-frequency lasers can be flexibly boosted to a power level of several tens of watts. Here, we demonstrate a high-power, single-frequency, and broadly tunable laser based on VECSEL technology. This device emits in the near-infrared around 1.06µm and exhibits high output power (>100 mW) with a low-divergence diffraction-limited TEM00 beam. It also features a narrow free-running linewidth of <400 kHz with high spectral purity (side mode suppression ratio >55 dB) and continuous broadband tunability greater than 250GHz (<15 V piezo voltage, 6kHz cutoff frequency) with a total tunable range up to 3THz. In addition, a compact design without any movable intracavity elements offers a robust single-frequency regime. Through fiber amplification, a tunable single-frequency laser is achieved at an output power of 50W covering the wavelength range from 1057 to 1066nm. Excess intensity noise brought on by the amplification stage is in good agreement with a theoretical model. A low relative intensity noise value of -145 dBc/Hz is obtained at 1MHz, and we reach the shot-noise limit above 200MHz.