Jonathan Y. Lee

Ultrafast optical switching based on nonlinear polarization rotation in silicon waveguides

We experimentally realize ultrafast all-optical switching in the 1.5-microm spectral region using cross-phase modulation inside a 5-mm long silicon waveguide. Modulation depths of up to 90% and switching window durations approximately 1 ps are achieved using 500-fs pump pulses with energies below 10 pJ.

Silicon carbide microdisk resonator

We demonstrate a silicon carbide (SiC) microdisk resonator with an intrinsic optical quality factor of 6.19×10(3), fabricated on the 3C-SiC-on-Si platform. We characterize the temperature dependence of the cavity resonance and obtain a thermo-optic coefficient of 2.92×10(-5)/K for 3C-SiC. Our simulations show that the device exhibits great potential for cavity optomechanical applications.

Slow-light dispersion in periodically patterned silicon microring resonators

We demonstrate a novel periodically patterned ring resonator evanescently coupled with a coupler waveguide (CWG) on a silicon-on-insulator platform. In order to optimize the coupling, we phase match the ring resonator and the CWG by tuning the width of the CWG. In the transmission spectra, we measure a high extinction ratio of more than 20 dB and achieve a group index of ~20 in the slow-light regime. Beating patterns in the calculated mode profiles suggest strong interference between degenerate modes. This device opens up the possibility of new applications in compact device integration in wavelength-division multiplexing system while reducing the in-band four-wave mixing cross talk.

High Q silicon carbide microdisk resonator

We demonstrate a silicon carbide (SiC) microdisk resonator with optical Q up to 5.12 × 104. The high optical quality, together with the diversity of whispering-gallery modes and the tunability of external coupling, renders SiC microdisk a promising platform for integrated quantum photonics applications.

Optical Kerr nonlinearity in a high-Q silicon carbide microresonator

We demonstrate a high-Q amorphous silicon carbide (a-SiC) microresonator with optical Q as high as 1.3 × 10(5). The high optical quality allows us to characterize the third-order nonlinear susceptibility of a-SiC. The Kerr nonlinearity is measured to be n2 = (5.9 ± 0.7) × 10(−15) cm(2)/W in the telecom band around 1550 nm. The strong Kerr nonlinearity and high optical quality render a-SiC microresonators a promising platform for integrated nonlinear photonics.

High-frequency and high-quality silicon carbide optomechanical microresonators.

Silicon carbide (SiC) exhibits excellent material properties attractive for broad applications. We demonstrate the first SiC optomechanical microresonators that integrate high mechanical frequency, high mechanical quality, and high optical quality into a single device. The radial-breathing mechanical mode has a mechanical frequency up to 1.69 GHz with a mechanical Q around 5500 in atmosphere, which corresponds to a fm · Qm product as high as 9.47 × 1012 Hz. The strong optomechanical coupling allows us to efficiently excite and probe the coherent mechanical oscillation by optical waves. The demonstrated devices, in combination with the superior thermal property, chemical inertness, and defect characteristics of SiC, show great potential for applications in metrology, sensing, and quantum photonics, particularly in harsh environments that are challenging for other device platforms.

High-Q silicon carbide photonic-crystal cavities

We demonstrate one-dimensional photonic-crystal nanobeam cavities in amorphous silicon carbide. The fundamental mode exhibits intrinsic optical quality factor as high as 7.69 × 104 with mode volume ∼0.60(λ/n)3 at wavelength 1.5 μm. A corresponding Purcell factor value of ∼104 is the highest reported to date in silicon carbide optical cavities. The device exhibits great potential for integrated nonlinear photonics and cavity nano-optomechanics.

3C-SiC Nanobeam Optomechanical Crystals

We report the first demonstration of high-quality (Q_i ~ 2.8-3.2×10³)3C silicon carbide photonic crystal nanobeams. With the strong optomechanical coupling (g_OM/2π ~ 100 GHz/nm), we observed clear optical transduction of the thermal mechanical motion of the coupled nanobeams.

Observation of spectral and temporal polarization oscillations of optical pulses in a silicon nanowaveguide

We observe both spectral and temporal oscillations in the polarization state of optical pulses propagating through a silicon nanowaveguide. The spectral oscillations are linear in nature and result from polarization-mode dispersion (PMD). The temporal oscillations are nonlinear in nature, and theoretical simulations clarify that they result from the combined effects of two-photon absorption generated free carriers and PMD.

Evanescent coupling to the slow-light modes in periodically patterned silicon microring resonators

We demonstrate evanescent coupling between a strip waveguide and a periodically patterned ring resonator in the slow light regime. Resonances with a group index >;22 are efficiently coupled with an extinction ratio of >;20 dB.