Injection seeders are devices that direct the output of small "seed"
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...
s into the
cavity of a much larger laser to stabilize the latter's output. Most seed lasers are stable,
single-frequency lasers that emit within the
linewidth
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
of the larger laser's
gain medium
The active laser medium (also called gain medium or lasing medium) is the source of optical gain within a laser. The gain results from the stimulated emission of photons through electronic or molecular transitions to a lower energy state from a h ...
. The single frequency encourages the larger laser to lase in a single
longitudinal mode
A longitudinal mode of a resonant cavity is a particular standing wave pattern formed by waves confined in the cavity. The longitudinal modes correspond to the wavelengths of the wave which are reinforced by constructive interference after man ...
, and the seed laser can also improve the laser's spatial profile and improve the
M2 parameter.
Seed lasers can be
continuous or pulsed. Seeding a pulsed laser can reduce variations in the output energy and timing (
jitter) from pulse to pulse, and smooth out temporal variations within the pulse. Many commercial lasers use a
laser diode
The laser diode chip removed and placed on the eye of a needle for scale
A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...
as a seeding source.
See also
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Laser construction
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Q-switching
Q-switching, sometimes known as giant pulse formation or Q-spoiling, is a technique by which a laser can be made to produce a pulsed output beam. The technique allows the production of light pulses with extremely high (gigawatt) peak power, much hi ...
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Mode locking
Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes r ...
References
Spotlight: Injection Seeding Technical University of Darmstadt
Bibliography
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Laser science
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