parasitic lasing (original) (raw)
Definition: unwanted laser operation in a laser or amplifier device
Categories: 
laser devices and laser physics, 
optical amplifiers
- laser physics
- cooperative lasing
- gain efficiency
- in-band pumping
- gain narrowing
- gain saturation
- Kuizenga–Siegman theory
- laser dynamics
- laser gain media
- laser transitions
- laser threshold
- lasing without inversion
- linewidth enhancement factor
- lower-state lifetime
- McCumber theory
- metastable states
- mode competition
- mode hopping
- modes of laser operation
- multiphonon transitions
- non-radiative transitions
- optical pumping
- output coupling efficiency
- parasitic lasing
- population inversion
- pulse generation
- radiation-balanced lasers
- radiative lifetime
- rate equation modeling
- reciprocity method
- relaxation oscillations
- single-frequency operation
- single-mode operation
- slope efficiency
- spatial hole burning
- spiking
- Stark level manifolds
- stimulated emission
- threshold pump power
- thresholdless lasers
- transition cross-sections
- twisted-mode technique
- ultrafast laser physics
- upconversion
- upper-state lifetime
- wavelength tuning
- (more topics)
Related: lasersoptical amplifiersamplified spontaneous emission
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DOI: 10.61835/z16 Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn
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Contents
What is Parasitic Lasing?
In lasers and amplifiers with high gain, laser operation may unintentionally take place on some closed beam path.
Examples of Cases With Parasitic Lasing
Some examples are briefly described in the following:
- In a rod or slab laser, total internal reflection and Fresnel reflection at the side faces of the laser crystal often lead to unexpected closed ring paths.
- In a thin-disk laser, the gain in directions transverse to the laser beam can be significantly higher than in the longitudinal direction, so that even weak reflections from the edges of the disk can lead to parasitic laser operation. As power scaling of a thin-disk laser involves a systematic increase in the ratio of transverse and longitudinal gain, parasitic lasing becomes a more serious challenge at higher power levels.
- In a fiber laser containing bulk optical elements, the Fresnel reflection from some fiber end may cause parasitic lasing even if the actual laser resonator is interrupted at some place (e.g. with a Q-switch). Similar effects can occur in a high-gain fiber amplifier. Such problems may be suppressed e.g. by using angled fiber ends, where the reflected light is not guided by the fiber core.
- Even from within an optical fiber, Rayleigh scattering can cause parasitic lasing.
The tendency for parasitic lasing is highest when there is a high unsaturated laser gain. This is the case e.g. in Q-switched lasers during the pumping period. In borderline cases, parasitic lasing may occur only at low pulse repetition rates, where the stored energy in the gain medium is higher.
Diagnosing Parasitic Laser Operation
It is not always simple to diagnose parasitic lasing. For example, when observing a laser crystal with an infrared viewer, it can be difficult to distinguish effects of parasitic lasing from those of parasitic reflections of laser light (without a closed beam path), or from pump light which may also be scattered in different directions, or from fluorescence.
For sufficiently high gain (e.g. several tens of decibels), there may also be amplified spontaneous emission (ASE). The optical spectrum usually exhibits sharp and unstable peaks in the case of parasitic lasing, whereas ASE leads to a spectrum with a smoother shape.
Effects of Parasitic Lasing
The primary detrimental effect of parasitic lasing is usually the unwanted extraction of energy, which leads to gain clamping and may thus prevent the intended lasing altogether or at least limit its power or the pulse energy. It is also possible that parasitic lasing leads to the emission of coherent light in unexpected directions, which can constitute a laser hazard.
Frequently Asked Questions
This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).
What is parasitic lasing?
Parasitic lasing is an unintended laser operation within a laser or optical amplifier. It occurs when high gain leads to lasing on an unintentional closed optical path, different from the intended one.
What causes parasitic lasing in high-gain systems?
What are the detrimental effects of parasitic lasing?
The primary negative effect is the unwanted extraction of energy, which leads to gain clamping. This can limit the output power and pulse energy of the intended laser beam or prevent lasing altogether. It can also create a laser hazard by emitting light in unexpected directions.
How can one distinguish parasitic lasing from amplified spontaneous emission (ASE)?
Parasitic lasing can be distinguished from amplified spontaneous emission (ASE) by examining the optical spectrum. Parasitic lasing typically causes sharp and unstable spectral peaks, whereas ASE results in a spectrum with a much smoother shape.
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