Experiments on modulation properties and optical feedback characteristics of laser diodes stabilized by an external cavity or injection locking

Abstract

In the wavelength range near 1.3-pm, single-mode operation of laser diodes is achieved by means of an external cavity and injection locking. The influence of digital modulation and optical feedback from a directly taper-coupled fiber is investigated.Lasers stabilized by injection locking showed excellent side-mode suppression at CW-operation but strong side modes when the laser was modulated. The frequency of the main mode is neither affected by modulation nor by optical feedback from the fiber.On the contrary the laser stabilized by an external cavity exhibited good side-mode suppression even when it was modulated. However, the frequency stability of the main mode was influenced severely by optical feedback and modulation. A transmission experiment over 21 km at a bit rate of 2.24Gbit/s showed that this simple stabilization method is sufficient for applications in optical wide-band IM-PCM transmission systems.

Improved intrinsic dynamic distortions in directly modulated semiconductor lasers by optical injection locking

“…On the other hand, according to our experiences, the fluctuation of the nonlinear harmonic powers is greatly suppressed by the injection locking, particularly for high modulation frequencies. The decreased sensitivity to external optical feedback in semiconductor lasers has been previously observed [17].…”

Theory and experiment of MEMS tunable lasers

“…Based on the Lamb's semi-classical laser theory [57], the state inside the FP cavity can be expressed by the field equation and rate equations as given by [61] ^4[G(n)-rK(0-yM»)-*(0+^" t , [32,33,62,74]. Tuning of the master can lead to the wavelength tuning of the slave (though tuning may not cover the full wavelength range).…”

“…For high-speed modulation (i.e. time domain), the injection locking can be used to assure single-mode operation [74,75] and to reduce the mode partition noise [76]. Additionally, it can significantly broaden the modulation bandwidth and flatten the modulation response [77,78].…”