Single-mode, All-Solid-State Nd:YAG Laser Pumped UV Converter
In this paper, the status of a high-energy, all solid-state Nd:YAG laser pumped nonlinear optics based UV converter development is discussed. The high-energy UV transmitter technology is being developed for ozone sensing applications from space based platforms using differential lidar technique. The goal is to generate greater than 200 mJ/pulse with 10-50 Hz PRF at wavelengths of 308 nm and 320 nm. A diode-pumped, all-solid-state and single longitudinal mode Nd:YAG laser designed to provide conductively cooled operation at 1064 nm has been built and tested. Currently, this pump laser provides an output pulse energy of >1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of <2. The single frequency UV converter arrangement basically consists of an IR Optical Parametric Oscillator (OPO) and a Sum Frequency Generator (SFG) setups that are pumped by 532 nm wavelength obtained via Second Harmonic Generation (SHG). In this paper, the operation of an inter cavity SFG with CW laser seeding scheme generating 320 nm wavelength is presented. Efforts are underway to improve conversion efficiency of this mJ class UV converter by modifying the spatial beam profile of the pump laser.
High energy, single-mode, all-solid-state and tunable UV laser transmitter
Summary form only given. For flight worthy and space-qualifiable systems, compact, conductively cooled, and solid-state design configuration is vital. The technical approach for the development of a reliable, robust and efficient diode-pumped Nd:YAG pump laser is based on an oscillator/amplifier design configuration. The first stage consisted of a ring oscillator generating up to 50 mJ/pulse and dual amplifiers. The first stage generated greater than 700 m/pulse. In the second stage, amplifiers were added to obtain output energy greater than 1.2 J/pulse. The important features of this all-solid-state pump laser are as follows: (a) injection seeded ring laser that improves emission brightness (M2), (b) diode-pumped zigzag slab amplifiers that allows robust and efficient design for use in space environment, (c) advanced E-O phase modulator material that allows high frequency cavity modulation for improved stability injection seeding, (d) alignment insensitive/boresight stable 1.0 mm cavity and optical bench for achieving stable and reliable operation, (e) conduction cooled operation that eliminates circulating liquids within cavity, and (e) space-qualifiable component designs that establishes a path to a space-based mission. The goal is to obtain nearly flat-top spatial beam profile to enhance the nonlinear conversion processes used to produce the UV output wavelengths. Our approach to the oscillator head design was to develop a design that demonstrated the key features needed for a flight system and that could be easily modified for an actual flight build pump laser. To this end, we developed a design that uses a bridge structure to mount and conductively cool the zigzag slab to a pedestal on which the pump diodes are mounted. Random selection of one or more amplifiers allows obtaining different levels of output energy. This pump laser system has the potential to generate greater than 1.2 J/pulse at 100 Hz.
Widely tunable narrow-linewidth nanosecond optical parametric generator with self-injection seeding
This paper reports a widely tunable narrow-linewidth nanosecond optical parametric generator (OPG) with a pulse-repetition rate of 10 kHz. The OPG consists of a 55-mm-long periodically poled lithium niobate crystal with a domain period of 29.5 μm. At an average pump power of 2.0 W the OPG emitted 0.33 W of signal power and 0.17 W of idler power. The wavelength and spectral width of the OPG are controlled by self-injection seeding. For this purpose, a small fraction of the OPG’s pulsed signal radiation is used as seed radiation for the next OPG pulse. In order to overlap in time the seed pulse with the succeeding pump pulse, the seed pulse is delayed by a 22-km-long single-mode fiber. For narrowing the spectrum of the seeded OPG output, the seed radiation is spectrally filtered by a tunable fiber Fabry–Perot interferometer (FFPI). The OPG signal radiation could be tuned from 1547 to 1605 nm by changing the OPG’s crystal temperature and by tuning simultaneously the FFPI. The corresponding idler wave tuned from 3157 to 3413 nm. Within the whole tuning range, the linewidth of the signal wave was less than 185 MHz. Compared to the 240-GHz linewidth of the free-running OPG, the linewidth of the seeded OPG is thus narrowed by more than three orders of magnitude. By tuning the FFPI, continuous wavelength tuning has been demonstrated within the gain spectrum of the OPG over a range of 820 GHz.