Single-Frequency Tunable IR Laser Development
The primary goal of the Phase II SBIR effort, funded by the Department of Commerce, Contract Number 50-DKNB-7-90140, was to follow an ambitious development path towards the demonstration of single-frequency operation of an all-solid-state Cr:YAG (Cr4+-doped Yttrium Aluminum Garnet) laser. This goal was achieved and significant additional progress has been made towards a better understanding of how to build single-frequency, broadly tunable Cr:YAG lasers. A brief summary of the work and accomplishments is provided in this section with more details provided in links to papers below.
A standing wave Cr:YAG resonator was designed, constructed and lasing action achieved, through pumping by a Q-Peak diode-pumped, 1047-nm Nd:YLF laser. The stability space of the resonator was investigated and optimized for maximum output. After some development effort, we obtained typical untuned output powers in the 1 W range with typical conversion efficiencies of 14% for all crystals.
To obtain tuning action single-, two-, and three-plate birefringent filters (BRF) were inserted in the resonator and the laser was tuned from 1360 nm to 1550 nm, a limit set by the output coupler bandwidth, with greater than 100 mW of output power. Earlier work with a single-plate BRF and a different optics demonstrated tuning out to 1610 nm.
Single-frequency operation was obtained in a unidirectional ring resonator with an optical diode that used a non-reciprocal polarization rotation in the Cr:YAG laser material, due to the Faraday effect, and a non-planar resonator geometry to provide the reciprocal polarization compensation. Tuning was obtained using a single-plate BRF and a solid, CaF2 etalon was added to ensure single-frequency operation. Up to 680 mW of single-frequency output power was obtained at the peak of the tuning curve with greater than 50 mW available from 1340 nm to 1554 nm.
To the best of our knowledge this work is the first such demonstration using Cr:YAG. All of the critical components and design challenges have been thoroughly investigated. The system performance demonstrated in this work is ideally suited to injection seeding of optical parametric oscillators, as was originally intended. Larger potential markets for the single-frequency Cr:YAG laser may be realized in telecommunications test instruments or near-infrared spectroscopy devices.
A paper presented at CLEO 2000 provides an excellent summary of our work. Two forms of the paper are available in the links below. One is a copy of the text, and the other is in the form of a Powerpoint presentation. The latter contains some material not included with the text.
Single-frequency operation of a Cr:YAG laser from 1332-nm to 1554-nm (Text)
Single-frequency operation of a Cr:YAG laser from 1332-nm to 1554-nm (Powerpoint)