Second‐Harmonic Generation in Integrated Photonics on Silicon

Abstract

This paper presents the recent progress on integrated second-order nonlinear waveguides on silicon substrates for second-harmonic generation. In particular, demonstrations of thin-film lithium niobate, III-V compound semiconductor and dielectric waveguides integrated on silicon substrates are reviewed. For completeness, the fundamentals of the nonlinear optical processes involved are briefly introduced. Methods demonstrated for phase matching, e.g., periodic poling and mode-shape modulation, in the compact integrated devices are discussed. Finally, an outlook for how integrated photonics may benefit from the progress in this field is provided.

Rejuvenating a Versatile Photonic Material: Thin‐Film Lithium Niobate

“…Another advantage is that the techniques discussed in this section are not limited to ferroelectrics, and in principal, can be applied to other nonlinear materials. [151] Detailed mathematical derivations for different phase matching methods can be found in ref. [121].…”

Towards On-Chip Self-Referenced Frequency-Comb Sources Based on Semiconductor Mode-Locked Lasers

“…The second functionality, required for the f -2 f referencing scheme, is efficient SHG. For a thorough review of SHG in heterogeneous integrated photonics, the reader is directed to [84] and for a discussion of appropriate figures of merit to [85]. Table 4 collects the most important demonstrations in integrated photonics.…”

“…Since the two are separated by an octave, in terms of frequency, this leads to the phase-matching condition being satisfied for a higher-order mode at the signal wavelength as for Si3N4, GaN and AlN cases in Table 4. This is suboptimal, as it compromises the mode-overlap between the pump and signal and thus overall conversion efficiency [84], as well as the mode-overlap between the signal short-wavelength part of supercontinuum (which is usually in the fundamental mode).…”

“…Finally, there is the thin-film equivalent of the commercially successful PPLN technology, where the phase matching is achieved through periodic-poling of the ferroelectric LN crystals [84,90,91]. Here, efficiencies of up to 4600% W−1cm−2 have been recently demonstrated for 1550 nm pump [85] and functionality for 2 μm pump has also been shown [92,93].…”

“…As mentioned, second harmonic was demonstrated on thin-film PPLN, reviews of which can be found elsewhere [84,85]. The first PPLN device on silicon substrates showed only 3 dB difference between the signal and the pump [90] and the recorded spectrum is shown in Figure 4d.…”