Slow and fast light: Controlling the speed of light using semiconductor waveguides

Abstract

We give an overview of slow-and fast-light effects in semiconductor active waveguides. Experimental and theoretical results are presented, emphasizing the physics of these phenomena and the limitations imposed by the carrier dynamical processes.A train of optical pulses injected into a quantum dot semiconductor optical waveguide, where the velocity is slowed down and the pulsewidth is reduced.

Tunable true-time delay of a microwave photonic signal realized by cross gain modulation in a semiconductor waveguide

“…These results share common features with slow light in SOAs mediated by coherent population oscillations. [10][11][12] In contrast, for the counter-propagating configuration (Fig. 3(b)) a tunable truetime delay from 0 to $10 ps is obtained over a large range of frequencies, extending from $5 to 35 GHz by tuning the input optical signal power.…”

“…In particular, slow light in active semiconductor waveguides can provide very fast tuning speed, compact size, and low power consumption. [10][11][12][13] Though microwave phase shifts beyond 360 have been experimentally demonstrated, 13 fundamental limitations 11,14 make it difficult to achieve true time delays over a broad bandwidth, e.g., several tens of GHz, by using slow light effects.…”

Slow-light enhanced absorption in a hollow-core fiber

“…Intuitively, slow-light propagation offers the photons longer time for interacting with the host medium, thus enabling enhanced sensitivity of interferometers and gyroscopes, enhanced non-linear interactions, enhanced spontaneous emission, and enhanced gain and absorption sensitivity, see e.g. [1][2][3][4][5][6][7]. Expressing the group velocity as v g = c/n g , the magnitude of the group index, n g , relative to that of a reference structure is often taken as a measure of the factor by which slow-light effects enhance light-matter coupling.…”

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.…”

“…1 illustrates the level schemes and corresponding susceptibilities for two schemes that may be used to realise light slow-down in semiconductors, i.e., electromagnetically induced transparency (EIT) [3,10] and coherent population oscillations (CPO) [12]. For a recent review of CPO effects in semiconductors please refer to [11]. The realisation of EIT requires a discrete level structure, as found in semiconductor quantum dots.…”