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Source: MDPI
Gain Switching in Laser Technology
Gain switching is a method used in laser technology for pulse generation by quickly modulating the laser gain through the pump power. When a high pump power is rapidly applied to a laser, the laser emission is delayed, starting with weak fluorescence light that needs to be amplified in the resonator before being extracted as a short pulse.
Pulse Build-up Time and Duration
The pulse duration obtained through gain switching can be shorter than both the pump pulse and the upper-state lifetime of the laser. The build-up time of the pulse is influenced by the pump pulse energy, with higher energies leading to shorter build-up times and consequently shorter required pump pulse durations. However, increasing the build-up time can also increase the output pulse duration.
Gain-switched vs. Free-running Operation
Gain-switched lasers differ from free-running lasers in that the pulsed output is a result of modulating the laser gain. In some cases, lasers with pulsed pump sources can exhibit similar behavior when the Q switch is omitted or disabled, leading to pulsed output, albeit with different characteristics.
Applications of Gain Switching
Gain switching can be applied to various types of lasers, including gas lasers, dye lasers, solid-state lasers, and laser diodes. Each type of laser has specific characteristics when operated in a gain-switched mode, allowing for a range of pulse durations and energies.
Advantages and Considerations
Gain-switched laser diodes offer advantages in adjusting pulse repetition rates and compactness compared to mode-locked lasers. However, they may exhibit larger timing jitter and fluctuations in pulse parameters. Combining gain-switched laser diodes with fiber amplifiers can generate pulses with higher energies and provide flexibility in pulse duration, shape, and repetition rate.
Conclusion
Gain switching is a versatile method for pulse generation in various types of lasers, offering control over pulse characteristics and flexibility in laser operation. Understanding the principles and applications of gain switching can help in optimizing laser performance for specific applications in research, industry, and technology.
Source: MDPI
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