Sample interview questions: What are some common techniques for achieving single-frequency laser output?
Sample answer:
Common Techniques for Achieving Single-Frequency Laser Output
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Intracavity Etalons: Fabry-Perot etalons or other resonant elements are placed within the laser cavity to selectively enhance the desired longitudinal mode.
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Diffraction Gratings: A diffraction grating external to the laser cavity can be used to disperse the different longitudinal modes and extract a single mode.
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Injection Seeding: A low-power, single-frequency laser beam is injected into the cavity to force the laser to oscillate at the seed frequency.
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Mode-Locking: This technique synchronizes the phases of multiple longitudinal modes to produce a train of ultrashort pulses, which can then be filtered to obtain a single frequency.
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Phase Conjugation: Four-wave mixing or other phase-conjugation techniques can generate a phase-conjugate wave that compensates for optical phase aberrations and suppresses unwanted modes.