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We demonstrate amorphous Ge0.92Sn0.08 surface illuminated metal-semiconductor-metal (MSM) photodetectors on flexible substrates for visible wavelength. Photodetection at 633 nm is achieved with an I-V response up to 10-4 A for a 2 V bias voltage. Different evaporation rate effects on the amorphous GeSn MSM photodetector are examined. Bending/strain effects on device performance were studied by evaluating the current density versus voltage characteristics. Amorphous GeSn thin film deposition on polyethylene terephthalate flexible substrate and Ni/Au-GeSn-Ni/Au MSM photodetector finger pattern deposition were performed via thermal evaporation. Photocurrent and dark current densities of amorphous GeSn MSM photodetectors were obtained at 1.36 A/cm2 and 0.24 A/cm2, respectively, where the photocurrent to dark current contrast ratio was found to be equal to 5.6. We also examined the evaporation rate, strain, and bending effect.

The 53.125 Gbps transmission is experimentally investigated over a next-generation wideband multimode optical fiber (NG-WBMMF) using transmitter optical sub-assemblies (TOSAs) and wideband receiver optical sub-assemblies (ROSAs) developed for 25 Gbps short wavelength division multiplexing (SWDM) operation. A commercial 100 Gbps four-level pulse amplitude modulation integrated circuit (PAM4 IC) evaluation kit with real-time digital signal processing (DSP) is used. Dual wavelength transmission (2 λ × 53.125 Gbps) tests over 300 m of NG-WBMMF are carried out for the wavelength pairs 850, 880 nm and 910, 940 nm with a 4 × 1 optical MUX/DeMUX in the link. Measured pre-forward error correction (FEC) bit error ratio (BER) below the KP4 FEC threshold of 2.4 × 10–4 indicates the feasibility of 100/200 Gbps transmission over NG-WBMMF using a PAM4 chipset with real-time DSP. Single wavelength transmission (1 λ × 53.125 Gbps) using long wavelength TOSAs at 976 and 1066 nm is also studied. Pre-FEC BER below 2.4 × 10–4 is achieved over 300 m at 976 nm and 200 m at 1066 nm. Single wavelength tests from 850 to 940 nm had the same results as the 976 nm wavelength. Thus, this is the first experiment which shows the potential of 400 Gbps transmission with eight SWDM wavelength windows over a single NG-WBMMF using SWDM TOSAs, ROSAs, and commercial 100 Gbps PAM4 chipset.

Two system transmission experiments are reported which indicate the feasibility of transmitting an aggregated speed of >200 Gb/s over a single next-generation wide-band multimode optical fiber (NG-WBMMF) using a shortwave wavelength division multiplexing (SWDM) and a four-level pulse amplitude modulation (PAM4), using optics rated for ${\text{25 Gb/s}}$ NRZ operation. The first experiment leverages predistorted KR4 ${\text{51.5625 Gb/s}}$ electrical PAM4 signaling generated by an arbitrary waveform generator to drive SWDM TOSAs at 850, 880, 910, and 940 nm. The received optical PAM4 signals are then post processed offline with linear equalizers to improve the eye quality. Detailed analysis of the height and width of the received optical eyes indicates an aggregated ${\text{206.25 Gb/s}}$ speed is achievable on a single NG-WBMMF beyond 150 m. In the second experiment, a commercial PAM4 IC evaluation kit with real-time digital signal processing is adopted to generate and detect PAM4 signals at KP4 FEC rate of ${\text{53.125 Gb/s}}$ per wavelength. The SWDM wavelength range is extended with additional tests at 980 nm. Pre-FEC BER below threshold of ${\text{2.4}}\times {\text{10}}^{-4}$ is achieved up to 300 m across all five wavelengths demonstrating an aggregated speed of ${\text{265.625 Gb/s}}$ over a single MMF.

Statistical studies on the scanning electron microscope (SEM) images of two-dimensional photonic crystal (PhC) slab cavities show that fabrication errors in the size and position of etched air holes follow Gaussian distribution. The influences on the characteristics of PhC cavities are then investigated and compared with those caused by fabrication error with widely-accepted uniform distribution through finite-difference time domain (FDTD) simulation. As expected, Gaussian distribution in fabrication error has more significant impact on cavity characteristics than uniform distribution simply by their difference in the fourth moment.