Terahertz all-optical modulation in a silicon–polymer hybrid system

Abstract

Although gigahertz-scale free-carrier modulators have been demonstrated in silicon, intensity modulators operating at terahertz speeds have not been reported because of silicon's weak ultrafast nonlinearity. We have demonstrated intensity modulation of light with light in a silicon-polymer waveguide device, based on the all-optical Kerr effect-the ultrafast effect used in four-wave mixing. Direct measurements of time-domain intensity modulation are made at speeds of 10 GHz. We showed experimentally that the mechanism of this modulation is ultrafast through spectral measurements, and that intensity modulation at frequencies in excess of 1 THz can be obtained. By integrating optical polymers through evanescent coupling to silicon waveguides, we greatly increase the effective nonlinearity of the waveguide, allowing operation at continuous-wave power levels compatible with telecommunication systems. These devices are a first step in the development of large-scale integrated ultrafast optical logic in silicon, and are two orders of magnitude faster than previously reported silicon devices.

Metawaveguide for Asymmetric Interferometric Light-Light Switching

“…Here, a relatively small value of δ ¼ 2 was chosen to obtain a reasonable transmission efficiency and ensure that fabrication imperfections do not make the system deviate strongly from the designed CPA condition. We find that the intensity ratio ξ is given by ðδ þ 1Þ=ðδ − 1Þ, leading to ξ of 3∶1 between the strong signal beam and the weak control beam [33], which is in contrast to the previous approaches of controlling light with light using both linear and nonlinear strategies [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…DOI: 10.1103/PhysRevLett.117.193901 Effective light-light switching promises optical information processing, which has been a long-standing driving force for high-speed and energy-efficient optical networks. Strong optical modulations are initiated in nonlinear optical media by intense laser fields to enable switching of a weak signal, for example, intensity modulation of light by light has been demonstrated based on the all-optical Kerr effect [1][2][3][4][5][6]. Nevertheless, the high power requirement for the intense control or pump light becomes a significant barrier for practical applications.…”

Subpicosecond Optical Switching with a Negative Index Metamaterial

“…Due to generally weak ([X (2)]2 or X(3» optical nonlinearities, all-optical Kerr-effect and three/four-wave mixing modulators require macroscopic propagation lengths, from cm's in the case of periodically-poled LiNb0 3 (PPLN) 4 to km for fiber approaches. I Semicon ductor optical amplifiers (SOA) offer larger nonlinearities, but these are active devices adding optical noise and requiring significant additional area for carrier injection and heat dissipation.…”

Ultrafast nonlinear optical tuning of photonic crystal cavities

“…Free carriers can alternatively be swept out of the cavity by applying a potential across the device [6]. The second effect that can be used to modify the refractive index is the Kerr effect, which is promising for a variety of other applications [7,8] and, in principle, should result in modulation rates of 10 15 − 10 16 Hz. However, the free carrier effect is more easily achieved in the GaAs PC considered here.…”