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Multiwatt continuous-wave and Q-switched Er:YAG lasers at 1645 nm: performance issues
Da-Wun Chen1, Milton Birnbaum, Paul M Belden
1Photonics Technology Department, Electronics and Photonics Laboratory, The Aerospace Corporation, 2350 E. El Segundo Boulevard, El Segundo, California 90245, USA. dawun.chen@aero.org
Optics Letters
|May 19, 2009
Summary
Researchers investigated Er:YAG lasers at 1645 nm, reducing doping to minimize upconversion losses. A novel green emission from two-photon absorption was observed during Q-switched operation, with minimal impact on output.
Area of Science:
- Laser physics
- Materials science
- Quantum optics
Background:
- Erbium-doped Yttrium Aluminum Garnet (Er:YAG) lasers are crucial for various applications.
- Upconversion losses at low pulse repetition frequencies (PRFs) can limit Er:YAG laser efficiency.
- Optimizing doping levels is a common strategy to mitigate these losses.
Purpose of the Study:
- To investigate the continuous wave (cw) and Q-switched performance of Er:YAG lasers at 1645 nm.
- To improve laser efficiency at low PRFs by reducing the erbium doping concentration.
- To characterize a newly observed phenomenon of enhanced green emission.
Main Methods:
- Fabrication and testing of Er:YAG crystals with reduced erbium doping (0.25 at.%).
- Measurement of laser output power and efficiency under cw and Q-switched operation at 1645 nm.
- Spectroscopic analysis to identify the origin of enhanced green emission.
Main Results:
- A small improvement in efficiency was observed with the lower-doped Er:YAG material, indicating upconversion losses were not the primary cause of power loss at low PRFs.
- Enhanced green emission was observed during Q-switched operation, attributed to two-photon absorption of intracavity laser light.
- The output loss associated with this two-photon absorption process was found to be negligible.
Conclusions:
- Reducing Er:YAG doping to 0.25 at.% offers limited improvement for efficiency at low PRFs.
- Two-photon absorption leading to green emission is a novel phenomenon in 1645 nm Er:YAG lasers during Q-switched operation.
- This green emission does not significantly impact the primary laser output.
