Traveling Wave Geometry Research Articles

Broadband waveguide-integrated superconducting single-photon detectors with high system detection efficiency

Fast and efficient detection of single photons with high timing accuracy is a crucial requirement in most quantum optics experiments and enables novel sensing and imaging solutions. Superconducting nanowire single-photon detectors (SNSPD) achieve technology-leading performance in terms of detection efficiency, dark count rate, timing jitter, and detector dead times. However, conventional SNSPDs with high system detection efficiency typically rely on resonant enhancement of the absorption efficiency, thus only achieving attractive detector benchmarks over narrow spectral windows. Waveguide-integrated SNSPDs allow for leveraging the wideband material absorption in superconducting nanowires by absorbing light in a traveling-wave geometry but have been limited to low system detection efficiencies due to interface losses when coupling to optical fibers. Here, we show how high system detection efficiencies of 22%–73% are realized over a broad wavelength range from 532 nm to 1640 nm in a single waveguide-integrated SNSPD device. We accomplish efficient coupling between optical fibers and waveguide-integrated nanowire detectors by employing a 3D interface, produced in direct laser writing, that relies on total internal reflection for achieving a broad transmission bandwidth. We further find low timing jitter of 25.7 ps and detector decay times of 9.8 ns, allowing for single-photon counting with high repetition rates up to 100 MHz. Our work paves the way for an efficient single-photon detector solution that combines the spectral requirements of an extremely wide range of quantum optics experiments in a single device. The coupling approach and SNSPD-integration with nanophotonic circuits are further well-suited for realizing large-scale detector arrays.

Amorphous superconducting nanowire single-photon detectors integrated with nanophotonic waveguides

Future applications in integrated quantum photonics will require large numbers of efficient, fast, and low-noise single-photon counters. Superconducting nanowire single-photon detectors made from amorphous material systems are best suited to meet these demands, but the integration with nanophotonic circuits has remained a challenge. Here, we show how amorphous molybdenum silicide (MoSi) nanowires are integrated with nanophotonic silicon nitride waveguides in traveling wave geometry. We found a saturated on-chip detection efficiency of (73 ± 10) % for telecom wavelength photons and the sub-10 Hz dark count rate at a temperature of 2.1 K, which allows for operation in robust, compact, and economic cryogenic systems. Applications requiring fast counting will benefit from the sub-5 ns recovery times of our devices that we combine with 135 ps timing accuracy. Achieving this performance with waveguide-integrated amorphous superconductors is an important step toward enabling high yield fabrication of competitive single-photon detectors on a large variety of nanophotonic material systems.

Matrix of Integrated Superconducting Single-Photon Detectors With High Timing Resolution

We demonstrate a large grid of individually addressable superconducting single photon detectors on a single chip. Each detector element is fully integrated into an independent waveguide circuit with custom functionality at telecom wavelengths. High device density is achieved by fabricating the nanowire detectors in traveling wave geometry directly on top of silicon-on-insulator waveguides. Our superconducting single-photon detector matrix includes detector designs optimized for high detection efficiency, low dark count rate and high timing accuracy. As an example, we exploit the high timing resolution of a particularly short nanowire design to resolve individual photon round-trips in a cavity ring-down measurement of a silicon ring resonator.

Continuous-wave pump-enhanced optical parametric oscillator with ring resonator for wide and continuous tuning of single-frequency radiation

We demonstrate a PPLN based pump-enhanced, singly-resonant optical parametric oscillator configured in a traveling wave geometry and pumped by a Ti:sapphire laser. The inclusion of a low finesse etalon within the OPO cavity stabilizes the signal frequency, and rotation of the etalon allows this frequency to be systematically hopped from axial mode to nearest neighbor axial mode over the entire free spectral range of the etalon (83GHz). Tuning of the pump frequency allows the signal frequency to be smoothly tuned over a cavity free spectral range. More than 35mW of single frequency idler power was generated in the spectral range 2800-3000nm for 600mW pump power. The superiority of traveling wave over standing wave geometries in these regards is discussed.

All-solid-state picosecond tunable source of near-infrared radiation

A quasi-cw diode-pumped Nd:YAG laser, mode locked by a nonlinear mirror and stabilized by an acousto-optic modulator, has been developed that generates 31-ps, 23-microJ pulses. Employing this source with a periodically poled lithium niobate crystal in a traveling-wave geometry, we obtained extracavity frequency conversion with pump depletion of as much as 62% in the near infrared (1.46- 1.56 microm) with a pulse spectral width of 1.5nm and a beam quality M(2)=1.7.

Lasing at 79 nm in nickellike neodymium

Using a series of 150-ps pulses from the Nova laser to illuminate neodymium slab targets, we observe a 38-psduration lasing pulse at 7.906 nm in nickellike neodymium on the J = 0 ? 1, 4d ? 4p transition. To overcome the low gain in this system, we used a traveling-wave geometry in conjunction with two slab targets that were coupled lengthwise to increase the effective length and whose surfaces were curved to compensate partially for refraction effects.

Traveling-wave excitation of the Ar ii shake-up laser at 4765 nm

We describe the construction and operation of a single-pass laser in Ar ii at 476.5 nm pumped by soft x rays from a laser-produced plasma. Temporal and spatial coherence properties have been characterized by means of a variety of experimental techniques. We use a 5-J, 100-ps, 1053-nm laser pump pulse in a traveling-wave geometry to measure a maximum output energy of 550 μJ. The aspect ratio of the unsaturated gain region directly affects the divergence of the output laser beam, resulting in a half-angle divergence of 10 mrad for 10 cm of excitation length. A small-signal gain coefficient of 2.1 cm−1 was observed, with the onset of saturation occurring after just 2 cm of excitation.

Pulsed Microwave Processing of High-TC Superconducting Films

ABSTRACTWe have used 2.0-μsec microwave pulses at a frequency of 2.856 GHz to rapidly heat thin amorphous yttrium-barium-copper-oxide (YBCO) films deposited onto silicon substrates. The samples were irradiated inside a WR-284 waveguide by single-pass TE10 pulses in a traveling wave geometry. X-ray diffractometry studies show that an amorphous-to-crystalline phase transition occurs for incident pulse powers exceeding about 6 MW, in which case the amorphous YBCO layer is converted to Y2BaCuO5. Microscopy of the irradiated film reveals that the phase transition is brought about by melting of the YBCO precursor film and crystallization of the molten layer upon solidification. Time-resolved in situ experiments of the microwave reflectivity (R) and transmissivity (T) show that there is an abrupt change in R for microwave pulse powers exceeding the melt threshold, so that measurements of R and T can be used to monitor the onset of surface melting.

Saturation of the Xe iii 109-nm laser using traveling-wave laser-produced-plasma excitation

We describe the construction and operation of a 109-nm, photoionization-pumped, single-pass laser in Xe III. The laser is pumped by soft x rays emitted from a laser-produced plasma in a traveling-wave geometry. Using a 3.5-J, 300-psec, 1064-nm laser pump pulse, we measure a small-signal gain coefficient of 4.4 cm(-1) and a total small-signal gain of exp(40). The laser is fully saturated and produces an output energy of 20 microJ in a beam with 10-mrad divergence.

Theoretical and experimental analysis of infrared dye-laser action in a traveling-wave pumping geometry

A rate-equation model for the laser action of infrared dyes is introduced. An extended four-level scheme is used to describe the photophysical processes in the dye molecules. The dye is excited by a single picosecond pulse in the traveling-wave geometry. The spectral and temporal properties of the picosecond dye-laser emission and the gain curve of the system are calculated. The numerical results are compared to experimental data. The theoretical model is in good quantitative agreement with the experiment.