Slow-to-fast light using absorption to gain switching in quantum-well semiconductor optical amplifier

Abstract

Room temperature quantum-well semiconductor optical amplifier with large input power is utilized in both the absorption and gain regime as an optical group delay and advance (slow and fast light), respectively. Material resonance created by coherent population oscillation and four wave mixing is tuned by electrical injection current, which in turn controls the speed of light. The four-wave mixing and population oscillation model explains the slow-to-fast light switching. Experimentally, the scheme achieves 200 degrees phase shift at 1 GHz, which corresponds to 0.56 delay-bandwidth product. The device presents a feasible building block of a multi-bit optical buffer system.

Widely Tunable Microwave Photonic Notch Filter Based on Slow and Fast Light Effects

“…2 also shows that the phase sensitivity is different over the whole tuning range, 12 phase shift due to a 5-mA current change at the injection current of around 170 mA and 2 phase shift due to the same current change at around 90 or 230 mA. The solid lines are numerical results, calculated using a four-wave mixing model appropriate for semiconductor waveguides [14], [18], and show good agreement with the experimental results. In [19], we have already shown that the optical filtering technique can increase the bandwidth of the phase shifter to at least 15 GHz, which means that this proposed microwave phase shifter can provide 360 phase shift at other microwave frequency bands.…”

“…On the other hand, the use of slow and fast light effects based on the physical phenomena of electromagnetically induced transparency and coherent population oscillations (CPO) [12] [13], to achieve a microwave phase shifter [14]- [18], has received considerable attention lately. In particular, semiconductor-based devices provide advantages such as the possibility of integration, low power consumption, and operation at room temperature.…”

“…In particular, semiconductor-based devices provide advantages such as the possibility of integration, low power consumption, and operation at room temperature. Many results of controlling the microwave phase of sine-modulated optical signals have been demonstrated [16]- [19], which include a 120 phase shift at the modulation frequency of 4 GHz in two semiconductor optical amplifier-electroabsorber (SOA-EA) pairs [17] and 200 phase shift at 1 GHz in a 2.5-mm quantum-well SOA [18]. In [19], we reported that optical filtering can exploit the refractive-index dynamics of the SOA to not only largely enhance the phase slow-down effect, but also greatly increase the available bandwidth from a few to tens of gigahertz.…”

Theory of Optical-Filtering Enhanced Slow and Fast Light Effects in Semiconductor Optical Waveguides

“…Here, we estimated the phase shifting in the absorption/gain regime with the assumption of constant carrier lifetime and saturation power, Although the absolute scaling of the phase shift will be different for realistic varying values of carrier lifetime and saturation power for different electrical bias/current control, the results qualitatively indicate the properties of phase delay/advance by electrical bias/current control. By tuning the SOA from the gain regime into absorption regime, the sign of the phase shift changes from negative (fast light) to positive (slow light) without optical filtering [9]. By blocking the blue-shifted sideband, we observe a large phase delay in the absorption regime and a phase advance in the gain regime.…”

Exploring carrier dynamics in semiconductors for slow light

“…Practical applications, e.g. within microwave photonics [2] and optical communications, favour a technology which allows cheap and compact devices with potential for integration and recent results on semiconductor waveguides indicate a strong potential [3][4][5][6][7][8][9][10][11]. Fig.…”