Mechanism for reducing recovery time of optical nonlinearity in semiconductor laser amplifier

Abstract

We propose and demonstrate a novel scheme to reduce the recovery time of optical nonlinearity in a semiconductor laser optical amplifier driven under a loss condition for the signal light pulse. Additional light, which is set at a transparency wavelength in the active layer, promotes stimulated recombination of excess carriers induced by the absorption of the signal light. This scheme excludes any additional carrier transport mechanism and nonradiative recombination and hence generation of heat. The principle of operation is experimentally verified by measuring time-domain transmission variance using a pump–probe method. A drastic reduction of the excess-carrier lifetime to less than 70 ps was confirmed.

Demonstration of optical noise reduction by semiconductor optical amplifier with CW assist light

“…Moreover, the stimulated emission due to the CW assist light scheme allows us to overcome the caturier liktime limit, hence the high-speed operation can be realized. [6] In this paper, affer a brief description of the structure and the absoiption characteristics ofthe SOA as an NRD, we present an experimental confirmation of the improvement of receiver sensitivity by the noise reduction efect using the absorption nonlinearity. On the other hand, the error probability can also be improved due to the noise redistribution when we employ tlie same NRD in the way o f a transmission path instead of just behre the receiver.…”

Optical nonlinearities in semiconductor optical amplifier and electro-absorption modulator: their applications to all-optical regeneration

“…Another way to shorten the gain recovery time is to increase the optical power in the device either by an internal light such as a gain-clamped SOA [2] or by an external light. [3][4][5][6][7] In the latter case, one can set the external (assist) light conditions independently of the SOA conditions. Transparent assist light, which tends to clamp the transparent wavelength of the SOA to its wavelength at the steady state, serves to dynamically stabilize the gain characteristics of the SOA due to its absorption when an injected control pulse light instantaneously suppresses the SOA gain as shown in Fig.…”

Effect of assist light on XGM-based wavelength-conversion using SOAs

“…The operating speed in an ordinary SOA is usually about 10 GHz [5] and improving the response speed becomes an issue. Recently, the ability to substantially improve the SOA response speed has been reported by having CW light (assist light), which differs from the signal light from outside of the SOA, incident near the transparent wavelength in the SOA gain spectrum [6]. However, typically in traveling-wave SOAs, a carrier density distribution in the propagation direction of the light develops as the signal light is amplified.…”