We present our next-generation micro-integrated diode laser modules. Based on the ECDL-MOPA concept, the modules allow independent tuning of emission frequency and output power. They currently operate at 689, 767, 780 and 794 nm, but can also be adapted for other wavelengths. The modules achieve mode-hop-free tuning even beyond the free spectral range of the laser. Additionally, we realized a Bragg grating based frequency reference using the same technology. It demonstrates high stability and a wide tuning range. Currently, we expand the application of the technology towards distribution modules that efficiently split and shift laser signals for seamless transmission.
We present design and first performance results of an airborne differential absorption lidar laser transmitter that can measure CO2 and water isotopes at different wavelengths around 2 µm with the same setup. This laser will be integrated into an airborne lidar, intended to demonstrate future spaceborne instrument characteristics with high-energy (several tens of millijoules nanosecond-pulses) and high optical frequency-stability (less than a few hundreds of kilohertz long-term drift).
The transmitter consists of a widely tunable OPO with successive OPA that are pumped by a Nd:YAG MOPA and generates the on- and offline wavelength of the addressed species with narrow bandwidth.
We present our activities on the development of narrow linewidth tunable optical parametric sources and their integration in lidar systems. In particular, we present different implementations of the nested cavity optical parametric oscillator (NesCOPO) that enables tunable single-frequency emission from the SWIR to the LWIR, when pumped by a fixed or a tunable wavelength laser beam. We show how to amplify the output energy and while preserving the spectral linewidth to perform standoff detection of greenhouse gases and toxic chemicals with direct detection lidars.
We report on the current design and preliminary developments of the airborne Lidar Emitter and Multi-species greenhouse gases Observation iNstrument (LEMON), which is aiming at probing H2O and its isotope HDO at 1982 nm, CO2 at 2051 nm, and potentially CH4 at 2290 nm, with the Differential Absorption Lidar method (DIAL). The infrared emitter is based on the combination of two Nested Cavity OPOs (NesCOPOs) with a single optical parametric amplifier (OPA) line for high-energy pulse generation. This configuration is enabled by the use of high-aperture periodically poled KTP crystals (PPKTP), which provide efficient amplification in the spectral range of interest around 2 μm with slight temperature adjustments. The parametric stages are pumped with a Nd:YAG laser providing 200 mJ nanosecond double pulses at 75 Hz. According to parametric conversion simulations supported by current laboratory experiments, output energies in the 40 - 50 mJ range are expected in the extracted signal beam whilst maintaining a good beam quality (M² < 2). The ruler for all the optical frequencies involved in the system is planned to be provided by a GPS referenced frequency comb with large mode spacing (1 GHz) against which the emitter output pulses can be heterodyned. The frequency precision measurement is expected to be better than 200 kHz for the optical frequencies of interest. The presentation will give an overview of the key elements of design and of preliminary experimental characterizations of sub-systems building blocks.
We present progress in high power GaAs-based single-pass semiconductor tapered optical amplifiers and modules tailored for coherent beam combining (CBC) in master-oscillator power-amplifier configuration. Amplifier design is first studied, by varying device geometry and epitaxial structure in 976nm devices. Epitaxial structures with large vertical near field and low wave-guiding from the active region enable higher CBC efficiency. However, changes to in-plane geometry did not improve performance. Overall, CBC of tapered amplifiers is stable, reproducible and robust, motivating next the development of 1064nm CBC-ready stand-alone sub-modules. Design, construction and test results from the pilot-series fabrication of these amplifier modules are presented.
High brightness diode laser beam combining techniques are in demand for efficient high power nonlinear conversion. Coherent beam combining (CBC) is the only method that has the potential for brightness scaling by maintaining one single narrow spectral linewidth. CBC in a master oscillator power amplifier (MOPA) configuration using a small number of efficiently cooled tapered amplifiers is a promising approach for efficient brightness scaling in a simple architecture. We present the application of such a source based on CBC of three tapered amplifiers seeded by a DFB laser at λ = 976 nm for second harmonic generation (SHG). A maximum power of 2.1 W at 488 nm was generated by SHG in a MgO:PPLN bulk crystal limited by thermal effects. A clear benefit of the beam clean-up resulting from the CBC setup was documented leading to an improved nonlinear efficiency. As part of our ongoing studies into further brightness scaling in CBC architectures, we present an experimental analysis of the phase dynamics of tapered amplifiers in quasi continuous operation (QCW) at high currents. Furthermore, we are investigating different amplifier designs for improved beam quality at high powers and therefore improved combining efficiency.
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