Space- and ground-based non-accelerated long lifetime data for ruggedized commercial NPRO lasers

Abstract

Lifetime data is presented for ruggedized commercial NPRO lasers used in the Tropospheric Emission Spectrometer (TES) Instrument on NASA's Aura Earth-orbiting spacecraft, including 20 years of data from two life test units on the ground, 12 years of on-orbit data from TES Laser A, and 2 years of on-orbit data from TES Laser B. The TES lasers are diode-pumped Non-Planar Ring Oscillator (NPRO) lasers using Nd:YAG crystals. Since accelerated life testing was not possible on the complete laser, early prototype lasers that had gone through thermal cycling and vibration testing were placed on non-accelerated life tests with the hope of gathering at least a couple of years of data before launch. Long-term lifetime data for hybrid laser systems in space applications is not abundant, and out of necessity, accelerated reliability testing is usually done over a relatively short time with a large number of devices. The data presented in this paper is unique as it tracks the optical power output over time of a total of four lasers on the order of decades rather than months or years. Two of the lasers have each been on life test for over 20 years on the ground and are still operating, and the other two lasers have been on-orbit for 14 years. TES Laser A was still operating when the TES Instrument was decommissioned in January 2018. Therefore, the data presented covers over 450,000 non-accelerated device-hours, with 23% of those hours being in space.

A dual-frequency fundamental-mode NPRO laser for low-noise microwave generation

“…We finally show the frequency tunability of the microwave signal by strain (piezo) and temperature (thermoelectric cooler, TEC), respectively. Considering NPRO lasers have been successfully applied in industry [18], scientific applications [19] and space missions [20][21][22][23][24], we believe our investigations could facilitate NPRO-based microwave sources used in these areas.…”

“…The temperature tuning coefficient is given to be -60.5±0.1 kHz/K.The temperature-tuning of the microwave frequency can be explained by the response of the FSR of the ring resonator to temperature. First, the FSR is a function of refraction of n of the gain medium and ring resonator length of L. c FSR nL (22)…”