Carbon Nanotube Far Infrared Detectors with High Responsivity and Superior Polarization Selectivity Based on Engineered Optical Antennas

Single-wall carbon nanotube (SWCNT) thin films are promising for sensitive uncooled infrared detection based on the photothermoelectric effect. The SWCNT film is usually shaped into a belt and diversely doped to form a p-n junction at the center. Under the illumination of a focused incident light, the temperature gradient from the junction to the contacts leads to photoresponse. When the SWCNTs are aligned in one direction, the photoresponse becomes polarization selective. Although a typical bowtie antenna can improve the responsivity and polarization extinction ratio by deep-subwavelength light focusing, the absolute absorptance of the junction region is only 0.6%. In this work, the antenna was engineered for a higher light coupling efficiency. By integrating a bottom metal plane at a specific distance from the SWCNT film and optimizing the antenna geometries, we achieved ultra-efficient impedance matching between the antenna and the SWCNTs, thus the absorptance of the junction region was further enhanced by 21.3 times and reached 13.5%, which is more than 3 orders of magnitude higher than that of the device without the engineered antenna. The peak responsivity was further enhanced by 19.9 times and responsivity reached 1500 V/W at 1 THz. The resonant frequency can be tuned by changing the size of the antenna. Over the frequency range of 0.5 THz to 1.5 THz, the peak responsivity was further enhanced by 8.1 to 19.9 times, and the polarization extinction ratio was enhanced by 2.7 to 22.3 times. The highest polarization extinction ratio reached 3.04 × 105 at 0.5 THz. The results are based on the numerical simulations of the light and the thermal fields.

Compact Photonic Crystal Polarization Beam Splitter Based on the Self-Collimation Effect

We propose a new compact polarization beam splitter based on the self-collimation effect of two-dimensional photonic crystals and photonic bandgap characteristics. The device is composed of a rectangular air holes-based polarization beam splitting structure and circular air holes-based self-collimating structure. By inserting the polarization beam splitting structure into the self-collimating structure, the TE and TM polarized lights are orthogonally separated at their junction. When the number of rows in the hypotenuse of the inserted rectangular holes is 5, the transmittance of TE polarized light at 1550 nm is 95.4% and the corresponding polarization extinction ratio is 23 dB; on the other hand, the transmittance of TM polarized light is 88.5% and the corresponding polarization extinction ratio is 37 dB. For TE and TM polarized lights covering a 100 nm bandwidth, the TE and TM polarization extinction ratios are higher than 18 dB and 30 dB, respectively. Compared with the previous polarization beam splitters, our structure is simple, the size is small, and the extinction ratio is high, which meets the needs of modern optical communications, optical interconnection, and optical integrated systems.

Simulation, Fabrication and Characterization of an Integrated Plasmonic Polarizer on Ti Diffused LiNbO3 Channel Waveguide

In this work the design, fabrication and characterization of a TE-pass plasmonic waveguide polarizer on Ti in-diffused channel waveguide fabricated on x-cut LiNbO3 substrate are reported. By deposition of MgF2 of 5nm thickness as the buffer layer and Au layer of about 30nm thickness as the cladding layer the polarization extinction ratio measured to be 32dB and insertion loss for TE mode was about 2dB in a single mode channel waveguide of 2.1cm length.

An ultra-flat, low-noise and linearly polarized fiber supercontinuum source covering 670 nm-1390 nm

We report an octave-spanning coherent supercontinuum (SC) fiber laser with excellentnoise and polarization properties. This was achieved by pumping a highly birefringent all-normaldispersion (ANDi) photonic crystal fiber with a compact high-power ytterbium femtosecond laserat 1049 nm. This system generates an ultra-flat SC spectrum from 670 nm to 1390 nm with apower spectral density higher than 0.4 mW/nm and a polarization extinction ratio of 17 dB acrossthe entire bandwidth. An average pulse-to-pulse relative intensity noise (RIN) down to 0.54%from 700 nm to 1100 nm has been measured and found to be in good agreement with numericalsimulations. This highly-stable broadband source could find strong potential applications inbiomedical imaging and spectroscopy where improved signal to noise ratio is essential.

An ultra-flat, low-noise and linearly polarized fiber supercontinuum source covering 670 nm-1390 nm

We report an octave-spanning coherent supercontinuum (SC) fiber laser with excellentnoise and polarization properties. This was achieved by pumping a highly birefringent all-normaldispersion (ANDi) photonic crystal fiber with a compact high-power ytterbium femtosecond laserat 1049 nm. This system generates an ultra-flat SC spectrum from 670 nm to 1390 nm with apower spectral density higher than 0.4 mW/nm and a polarization extinction ratio of 17 dB acrossthe entire bandwidth. An average pulse-to-pulse relative intensity noise (RIN) down to 0.54%from 700 nm to 1100 nm has been measured and found to be in good agreement with numericalsimulations. This highly-stable broadband source could find strong potential applications inbiomedical imaging and spectroscopy where improved signal to noise ratio is essential.

A polarization encoded photon-to-spin interface

We propose an integrated photonics device for mapping qubits encoded in the polarization of a photon onto the spin state of a solid-state defect coupled to a photonic crystal cavity: a “polarization-encoded photon-to-spin interface” (PEPSI). We perform a theoretical analysis of the state fidelity’s dependence on the device’s polarization extinction ratio and atom–cavity cooperativity. Furthermore, we explore the rate-fidelity trade-off through analytical and numerical models. In simulation, we show that our design enables efficient, high fidelity photon-to-spin mapping.