Electric field-induced second-order nonlinear optical effects in silicon waveguides

Abstract

The demand for nonlinear effects within a silicon platform to support photonic circuits requiring phase-only modulation, frequency doubling, and/or difference frequency generation, is becoming increasingly clear. However, the symmetry of the silicon crystal inhibits second order optical nonlinear susceptibility, χ (2) . Here, we show that the crystalline symmetry is broken when a DC field is present, inducing a χ (2) in a silicon waveguide that is proportional to the large χ (3) of silicon. First, Mach-Zehnder interferometers using the DC Kerr effect optical phase shifters in silicon ridge waveguides with p-i-n junctions are demonstrated with a V π L of 2.4Vcm in telecom bands (λ ω =1.58µm) without requiring to dope the silicon core. Second, the pump and second harmonic modes in silicon ridge waveguides are quasi-phase matched when the magnitude, spatial distribution of the DC field and χ (2) are controlled with p-i-n junctions. Using these waveguides, second harmonic generation at multiple pump wavelengths are observed with a maximum efficiency of P 2ω /Pω 2 =12%/W at λ ω =2.29µm in a 1mm long waveguide. This corresponds to a fieldinduced χ (2) =41pm/V, comparable to non-centrosymmetric media (LiNbO 3, GaAs, GaN).The field-induced nonlinear silicon photonics will lead to a new class of CMOS compatible integrated devices spanning from near to mid infrared spectrum.

Frequency comb generation in continuously pumped optical parametric oscillator

“…Our results open the way to a new class of devices which could efficiently provide OFCs in spectral regions, like the MIR, where comb sources are highly desirable but still difficult to achieve, and based on complex experimental configurations [21]. In this respect, it is worth mentioning AlGaAs or Si as promising materials which can be shaped in chip-scale waveguide devices, providing large intrinsic or induced second-order nonlinearity, fully exploitable through efficient quasi-phase matching schemes [57,58]. namics of optical frequency combs" and FIRB n. In this Appendix, starting from the infinite dimensional map, Eqs.…”

Integrated rare-Earth doped mode-locked lasers on a CMOS platform

“…Efficient strategies for suppression of Q-switched mode locking include either feedback stabilization of intracavity power via an intracavity loss modulator or feedback stabilization of gain via pump modulation and/or further optimization of intracavity pulse parameters and pulse shaping. Together with the other components developed on the same silicon photonics platform, such as octave-spanning continuum generation [27] and on-chip second harmonic generation via an electric-field-induced second-order nonlinearity (EFISH) in silicon [28], these lasers would enable frequency comb generation and optical frequency synthesis on a complete silicon photonics platform. …”

Photonic Integrated Microwave Phase Shifter up to the mm-Wave Band With Fast Response Time in Silicon-on-Insulator Technology

“…Additionally, by implementing the optical phase shifter in a p-n junction silicon rib waveguide exploiting fast carrier-depletion modulation effect, a small reconfiguration time of about 1 ns is achieved, which outperforms previous realizations in SOI technology based on thermo-optic effect. The relatively large insertion loss of the optical phase-shifter due to free-carrier absorption in doped waveguides could be eliminated using recently proposed approach for optical phase modulators based on ultra-fast DC Kerr effect in silicon [26]. The integration of germanium photodiodes provides improved chip functionality, by enabling the access of the phase-shifted microwave signal through electrical contacts, which ease the possible packaging of the device for practical system applications.…”