Emission Characteristics of a 1.5- <inline-formula> <tex-math notation="TeX">$\mu$</tex-math></inline-formula>m All-Semiconductor Tapered Master Oscillator Power Amplifier

Abstract

We present experimental results on the emission characteristics of a 1.5-m distributed feedback (DFB) tapered master oscillator power amplifier (MOPA) in a wide range of steady-state injection conditions, showing different dynamical behaviors. A detailed analysis of the optical and radio-frequency spectra has allowed the identification of three different emission regimes: i) stable amplified DFB emission, but with wavelength jumps when sweeping the injection currents; ii) multimode Fabry-Perot (FP) operation of the complete MOPA cavity; and iii) self-pulsed operation at frequencies between 5 and 8 GHz. The quasi-periodic occurrence of these emission regimes as a function of the injected currents is interpreted in terms of a thermally tuned competition between the modes of the master oscillator and the compound cavity modes. The physical origin of the wavelength jumps and of the alternation between regimes is discussed.Index Terms: High power semiconductor lasers, master oscillator power amplifier, multimode dynamics.

Wavelength Jumps and Multimode Instabilities in Integrated Master Oscillator Power Amplifiers at 1.5 <inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>m: Experiments and Theory

“…The explored injection conditions included a continuous variation of the PA section current for several fixed values of the MO current. In addition to other previously reported instabilities, our study revealed a different kind of instability that involves large (>10 nm) and sudden jumps in the emission wavelength of the MOPA [2], [4]. The instability occurs for low currents in the MO section, i.e., when the MOPA is close to threshold, and it appears and disappears in a quasi-periodic way as a function of the CW current in the PA section.…”

“…A detailed description of the investigated devices and of the experimental setup has been reported elsewhere [4] and therefore only the most important features are repeated here. We used commercial MOPAs with emission wavelength close to 1550 nm (QPC 4715-0000).…”

“…However, it is known that even when driven in the CW regime, a small residual reflectance of the MOPA front facet may induce a variety of emission instabilities for specific injection conditions [3], [4]. These instabilities manifest for instance in the appearance of ripples in the power-current (P-I) curves, arising as a consequence of the coupling between the modes of the full MOPA cavity and the MO modes [5].…”

“…We have recently reported a systematic experimental study of the emission instabilities occurring in 1.5 μm integrated MOPAs under a wide range of CW injection conditions [4]. The explored injection conditions included a continuous variation of the PA section current for several fixed values of the MO current.…”

Laser module based on monolithically integrated Mopas at 1.5 μm for space-borne lidar applications

“…Standard straight monolithically integrated MOPAs exhibit instabilities due to compound cavity effects arising from the residual reflectivity at the amplifier output facet [17,18]. In order to decrease the reflections at the facets, a simple method consists in tilting the device with regard to the facets.…”