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Photon-pair sources are the key devices for quantum photonic applications; most of them are optically pumped. Here we present our design of an electrically injected photon-pair source based a Bragg-reflection-waveguide (BRW) GaInP/AlGaInP quantum well laser and internal spontaneous parametric down conversion, targeting at the wavelengths near 1.3 μm for signal and idler photons. We establish a model that allows us to simulate the major characteristics of the device. Our work shows the feasibility to extend the demonstration of the electrically injected BRW photon-pair source at 1.57 μm [Boitier et al. , “Electrically injected photon-pair source at room temperature,” Physical Review Letters , vol. 112, no. 18, 2014, Art. no. 183901] to another technologically interested wavelength.

We demonstrate a compact and broadband 1 × 4 optical switch based on W2 photonic crystal waveguides (PCWs). The footprint of the W2 PCW is only 17.6 μm × 8 μm. An operation bandwidth of 15 nm ± 1 nm is implemented with an extinction ratio over 15 dB in each channel. By introducing the thermal insulation trench, the tuning efficiency is enhanced at least 77% in experiment. The experimental results indicate the potential of the proposed broadband thermo-optic switch in silicon on-chip interconnects.

Silicon slot waveguides operating at a wavelength of high silicon absorption are fabricated on silicon-on-insulator wafers. The measured transmission loss coefficient is as low as $6\sim 8$ dB/cm at 1064 nm, which is much lower than the material absorption. In addition, the bending loss of the slot waveguides is measured as $4.1\sim 4.6$ dB/180° with a bending radius of 15 $\mu \text{m}$ . Both the transmission and bending losses are analyzed and discussed. We believe that this work could pave the way to achieve all-silicon photonic integrated circuits, which are very promising for a future on-chip chemical/biological analysis.

Radially polarized orbital angular momentum (OAM) beams could be applied in optical manipulation and optical microscopy. An integrated OAM beam emitter with radially polarized radiation is proposed on shallow-ridge silicon microring with azimuthally distributed gratings etched on top of the ring waveguide. Two key structural parameters, the number of grating elements, and the dimension of each grating element are optimized by considering both the OAM order purity $(C_{p})$ and the total radiation efficiency $(\eta_{all})$ . With elaborate design, $C_{p} = \,\sim\!98\%$ , $ \eta_{all} =\, \sim\!49\%$ are achieved by simulations, and the calculated energy ratio between the far-field radially and azimuthally polarized component is more than 11 dB, which indicates that the radially polarized component is predominant in the radiated electromagnetic field.

A bandstop microwave photonic filter is experimentally demonstrated with integrated optical processor fabricated on silicon-on-insulator substrate. The optical processor consists of microrings and a Mach-Zehnder interferometer so that two bandstop responses are produced for processing two sidebands separately. With such a structure, tunable and reconfigurable bandstop MPFs can be easily realized by thermally tuning the resonant wavelength of microrings. According to the experimental results, the operating frequency and 10-dB bandwidth can be tuned within the range of 7-34 GHz and 1.85-4.55 GHz, respectively.

A four-channel integrated optical add/drop multiplexer is experimentally demonstrated on a silicon-on-insulator substrate. With the help of a parent-sub microring resonator structure, compact footprint, large free spectral range, and uniform channel spacing are achieved simultaneously. Through controlling the resonance matching between the parent and sub-rings through thermo-optic effect, each channel can be switched independently between the states of dropping and passing through. The thermal tuning efficiency is as high as 0.27 nm/mW. Typically, for dropping state, all four channels can be de-multiplexed to the drop ports with 2 dB drop loss, 18 dB through port extinction, and less than -20 dB channel crosstalk.

The effects of structure parameters and structural deviations on the characteristics of photonic crystal directional couplers (PCDCs) were analyzed through a systematic simulation study. The relationship between coupling characteristics and structure parameters was discussed. The results reveal that the remained power in the coupling region is detrimental to reducing the insertion loss of PCDCs, especially for the PCDCs with shorter coupling length. An improved structure, which increases the radii of air holes in the post coupling region, was proposed to suppress the remained power and reduce the insertion loss effectively. The influence of structural deviations, which is caused by fabrication imperfections and results in the mismatch between experimental results and theoretical predictions, was also investigated using statistical methods. The simulation results show that the air hole position misalignment perpendicular to the waveguide direction has the largest effect on the insertion loss of PCDCs, and reducing r/a is helpful to improving the robustness of PCDCs.

Optical gain spectra of InGaAsP MQW for photonic crystal waveguide (PCWG) were simulated by the method with considering the variation of group velocity and the natural broadening synthetically. The dependence of the first mode's gain maximum on the width of PCWG was discussed. To improve the mode characteristics and the gain performances in the 2-D PCWG with relative large width, we proposed a new structure by combining a microcavity inside the 2-D PCWG. Mode characteristics in proposed structure were analyzed and the transmission performance was simulated by the FDTD method. The simulation results show that improved longitudinal mode characteristics can be obtained even in the W3 PCWG with relative wide waveguide width because of the additional frequency selecting mechanism provided by the microcavity.

A compact thermo-optic switch based on the cutoff effect of slow-light mode of a tapered W1 photonic crystal waveguide (PCW) is demonstrated with an integrated microheater. Due to the low-group-index taper, the coupling loss of the slow-light PCW is reduced, and a high switching extinction ratio (ER) is attained. Moreover, three types of microheaters are evaluated for the power consumptions, heating transfer efficiency, and temperature uniformities, and an optimized slab microheater is utilized. As a result, low switching power of 8.9 mW and high ER of 23.5 dB are achieved experimentally, while the length of W1 PCW is only 16.8 μm.

A photonic crystal nanobeam cavity with stagger holes in InP/InGaAsP/InP heterostructure is proposed for ultrafast directly modulated nano-light-emitting diodes (nanoLEDs). With stagger holes, the quality factor Q can be engineered in the range of 102 ~ 104 while keeping a small mode volume (Veff). As a result, the modulation speed of nanoLEDs can be dramatically improved by a small Veff to enhanced spontaneous emission (SpE) rate and a moderate Q to counterbalance SpE lifetime and photon lifetime of the cavity. In our simulation, the direct modulation bandwidth could be higher than 60 GHz with optimal Q value of 2150 and Veff of 2.3( λ0/2n)3.