Title: Monolithic High Power Semiconductor Seed Lasers Near 2.05 μm
Presenting Author: Mahmood Bagheri
Organization: Jet Propulsion Laboratory
Co-Author(s): C. Frez, C. Borgentun, R. Briggs and S. Forouhar; Jet Propulsion Laboratory

Abstract:
This paper reports on the technology development and demonstration of a compact 2-µm monolithic fiber-pigtailed semiconductor seed laser. This laser development is intended to enhance the operability and applicability of IPDA (integrated path differential absorption) lidar systems for high spatial and temporal resolution CO2 airborne measurements as well as future Earth-orbiting CO2 measurement missions. The frequency agility and multi-format modulation capability of the proposed technology, its small size and compatibility with standard distributed feedback (DFB) lasers at the telecom band paves the way for adoption of the attractive 2.05 μm CO2 band in the already demonstrated lidar systems operating at the 1.57 μm band. Furthermore, the large tuning range of the proposed semiconductor laser (>150 GHz), and their high speed modulation capability at moderate power consumption (<2 W) would enable unprecedented high vertical range-finding resolution on lidar systems and would greatly enhance the performance of current lidar systems operating at 2.05 μm that utilize solid-state crystal lasers. Our 2.05 μm lasers are packaged inside a temperature controlled standard 14-pin butterfly package with a PM1950 Nufern output optical fiber (polarization maintain optical fiber with transmission between 1850 -2200 nm). A single element optical lens images the mode of the laser onto the facet of the optical fiber and an integrated single-stage optical isolator and anti-reflection (AR) coated optical elements suppress and minimize optical feedback into the laser cavity. The slope efficiency from end of the optical fiber is 0.055 mWmA-1 with more than 20 mW output power at 400 mA. The DFB lasers show single mode behavior with better than 50 dB of side-mode suppression ratio (SMSR) and exhibit stable and constant wavelength (λ) tuning by dλdT-1 = 0.18 nmK-1 over a large current and temperature range with excellent side-mode suppression ratios. The optical output shows a linear polarization along the slow axis of the optical fiber with better than 20 dB extinction over the operating current and temperatures. The large mode-hop free tuning range of these lasers covers multiple CO2 absorption lines. The current tuning capability enables a variety of high-speed frequency sequencing and switching formats. This is important for high precision CO2 lidar measurement schemes that require near-simultaneous measurements at multiple wavelengths in the vicinity of the target absorption line in order to infer column CO2 concentration.