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Two-mode beat phase noise of actively modelocked lasers
Optics Express
|June 5, 2009
Summary
Phase noise in actively mode-locked lasers is higher when beating two longitudinal modes compared to the full spectrum. This two-mode beating is less affected by RF oscillator noise, despite increased phase noise.
Area of Science:
- Optics and Photonics
- Laser Physics
Background:
- Actively mode-locked lasers are crucial for generating ultrashort pulses.
- Phase noise is a critical parameter affecting laser performance and applications.
- Understanding mode beating in lasers is essential for noise characterization.
Purpose of the Study:
- To develop an analytic expression for phase noise spectrum in two-mode beating.
- To compare phase noise characteristics of two-mode beating with full spectrum beating.
- To investigate the influence of RF oscillator noise on two-mode beating.
Main Methods:
- Derivation of an analytic expression for phase noise spectrum.
- Selection of two arbitrary longitudinal modes for beating.
- Experimental validation of the theoretical model.
Main Results:
- An analytic expression for the phase noise spectrum of two-mode beating was estimated.
- Two-mode beating exhibits higher phase noise than full spectrum beating, particularly at low offset frequencies.
- Two-mode beating noise is largely decoupled from RF oscillator noise to the first order.
Conclusions:
- The analytic model accurately describes phase noise in two-mode beating.
- Two-mode beating is a significant source of phase noise in actively mode-locked lasers.
- Noise characteristics differ substantially between two-mode and full spectrum beating.
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