Holographically fabricated out-of-plane blazed gratings and channel waveguides in silica for integrated free-space beam delivery.

Grating couplers are widely used in integrated optics to generate free-space beams and facilitate localized interactions with systems such as atom or ion traps. However, etched devices often exhibit small-scale inconsistencies; exacerbated by the high index contrast of the devices, this can lead to phase errors, limiting devices to a sub-millimeter scale. Here we present the first demonstration, to our knowledge, of tilted, out-of-plane blazed gratings in planar silica fabricated by UV inscription using a 213 nm laser.

Continuous ultraviolet to blue-green astrocomb.

Cosmological and exoplanetary science using transformative telescopes like the ELT will demand precise calibration of astrophysical spectrographs in the blue-green, where stellar absorption lines are most abundant. Astrocombs-lasers providing a broadband sequence of regularly-spaced optical frequencies on a multi-GHz grid-promise an atomically-traceable calibration scale, but their realization in the blue-green is challenging for current infrared-laser-based technology. Here, we introduce a concept achieving a broad, continuous spectrum by combining second-harmonic generation and sum-frequency-mixing in an MgO:PPLN waveguide to generate 390-520 nm light from a 1 GHz Ti:sapphire frequency comb.

Temperature-tunable UV generation using an Alexandrite laser and PPLN waveguides.

We present a simple and novel technique for achieving ultra-violet (UV) wavelength-tunable laser operation in the continuous-wave regime. Wavelength tunable operation in the near infrared is obtained from a compact two-mirror Alexandrite laser cavity by temperature tuning of the laser crystal. Second-harmonic-generation to the UV is then achieved at 376-379 nm and 384-386 nm by temperature tuning of a periodically-poled lithium-niobate (PPLN) waveguide.

Short single-frequency self-pulsing Brillouin-Raman distributed feedback fiber laser.

We demonstrate that the stimulated Brillouin scattering of a 250 mm long distributed feedback Raman fiber laser can self-pulse with repetition rates up to 7 MHz, pulse widths of 25 ns, and peak powers of 1.2 W. While both CW and pulsed lasing are produced from a bespoke grating at 1119 nm this laser design could be constructed at almost any wavelength, as the Raman and Brillouin gain regions are relative to the pump wavelength.

High power 739 nm VECSELs for future Yb ion cooling.

We present an operational characterization of a vertical-external-cavity surface-emitting laser emitting around 739 nm with over 150 mW in a single fundamental spatial mode. Results show that the laser is capable of oscillating on a single cavity axial mode at 740 nm for up to 22 mW. Tuning of the optical emission is shown to reach 737.

Upconversion detection of 1.25 Gb/s mid-infrared telecommunications using a silicon avalanche photodiode.

With an ever-increasing interest in secure and reliable free-space optical communication, upconversion detectors enabled through nonlinear optical processes are an attractive route to transmitting data as a mid-infrared signal. This spectral region is known to have a higher transmissivity through the atmosphere. In this work, we present an upconversion scheme for detection in the silicon absorption band using magnesium-oxide doped periodically poled lithium niobate to generate 21 mW of a 3.

213 nm laser written waveguides in Ge-doped planar silica without hydrogen loading.

In this paper we present the first example of waveguides fabricated by UV writing in non-hydrogen loaded Ge-doped planar silica with 213 nm light. Single mode waveguides were fabricated and the numerical apertures and mode field diameters were measured for a range of writing fluences. A peak index change of 5.

CW demonstration of SHG spectral narrowing in a PPLN waveguide generating 2.5 W at 780 nm.

Periodically poled lithium niobate (PPLN) waveguides are a proven and popular means for efficient wavelength conversion. However, conventional PPLN waveguides typically have small mode field diameters (MFD) (≲6 µm) or significant insertion and/or propagation losses, limiting their ability to operate at multi-watt power levels. In this work we utilise zinc indiffused PPLN ridge waveguides that have a larger MFD, favourable pump/SHG modal overlap, and low insertion losses.

Highly-chirped Bragg gratings for integrated silica spectrometers.

A blazed chirped Bragg grating in a planar silica waveguide device was used to create an integrated diffractive element for a spectrometer. The grating diffracts light from a waveguide and creates a wavelength dependent focus in a manner similar to a bulk diffraction grating spectrometer. An external imaging system is used to analyse the light, later device iterations plan to integrate detectors to make a fully integrated spectrometer.

Zinc-indiffused MgO:PPLN waveguides for blue/UV generation via VECSEL pumping.

We present the design and characterization of a zinc-indiffused periodically poled lithium-niobate ridge waveguide for second-harmonic generation of ∼390 light from 780 nm. We use a newly developed, broadband near-infrared vertical external-cavity surface-emitting laser (VECSEL) to investigate the potential for lower-footprint nonlinear optical pump sources as an alternative to larger commercial laser systems. We demonstrate a VECSEL with an output power of 500 mW, containing an intracavity birefringent filter for spectral narrowing and wavelength selection.

Two-photon quantum interference and entanglement at 2.1 μm.

Quantum-enhanced optical systems operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. However, to date, sources of entangled photons have been realized mainly in the near-infrared 700- to 1550-nm spectral window.

ZnO indiffused MgO:PPLN ridge waveguides.

We have demonstrated the first MgO:PPLN ridge waveguides based on ZnO indiffusion and dicing. The fabrication process utilizes ductile regime dicing of a planar waveguide layer producing second harmonic generation (SHG) devices with a near-symmetric sinc spectral profile, indicating highly uniform 40 mm long devices. A near circular pump mode is also obtained enabling efficient coupling to single mode telecommunication fibers.

Integrated polarizer based on 45° tilted gratings.

We report the first integrated implementation of a polarizer based on the use of 45° tilted gratings in planar waveguides. The waveguides and gratings are fabricated by direct UV writing in a hydrogenated germanium-doped silica-on-silicon chip. We experimentally demonstrate a polarization extinction ratio per unit length of 0.

Leaky mode integrated optical fibre refractometer.

A route to monitor external refractive indices greater than the core index of the waveguide is presented. Initial application utilizes an integrated optical fibre (IOF) platform due to its potential for use in harsh environment sensing. IOF is fabricated using a bespoke flame hydrolysis deposition process to fuse an optical fibre to a planar substrate achieving an optical quality, ruggedized glass layer between the fibre and substrate was fabricated.

Germanium-on-silicon waveguides operating at mid-infrared wavelengths up to 8.5 μm.

We report transmission measurements of germanium on silicon waveguides in the 7.5-8.5 μm wavelength range, with a minimum propagation loss of 2.

Nanoscale roughness micromilled silica evanescent refractometer.

We demonstrate machining of precision slots in silica with nanoscale roughness for applications in photonics. Using our in-house developed milling system we have achieved machined slots with surface roughness of 3.0 nm (Sa) and 17 µm depth of cut.

Compact, high-pulse-energy, picosecond optical parametric oscillator.

We report a high-energy optical parametric oscillator (OPO) synchronously pumped by a 7.19 MHz, Yb:fiber-amplified, picosecond, gain-switched laser diode. The 42-m-long ring cavity maintains a compact design through the use of an intracavity optical fiber.

High-power, variable repetition rate, picosecond optical parametric oscillator pumped by an amplified gain-switched diode.

We demonstrate a picosecond optical parametric oscillator (OPO) that is synchronously pumped by a fiber-amplified gain-switched laser diode. At 24W of pump power, up to 7.3W at 1.

Design and demonstration of direct UV-written small angle X couplers in silica-on-silicon for broadband operation.

Experimental demonstration of small angle (0.8 degrees-5 degrees ) direct UV-written X couplers in silica-on-silicon is presented. Maximum and minimum coupling ratios of 95%(+/-0.

Guided-wave second-harmonic generation in a LiNbO3 nonlinear photonic crystal.

We demonstrate twin-beam second-harmonic generation from telecommunications wavelengths in an optimized buried reverse proton exchanged planar waveguide made in 2D hexagonally poled LiNbO3. Experiments carried out with a nanosecond narrow-bandwidth, high-power fiber source thoroughly explored the response of the nonlinear photonic crystal device in terms of its power, wavelength, and angle tunability.

Physical observation of single step UV-written integrated planar Bragg structures and their application as a refractive-index sensor.

We present what is to our knowledge the first demonstration of a potentially low-cost refractive-index sensor based on UV processing. A channel waveguide and a Bragg grating are defined in a single UV processing step, resulting in a buried structure with a well-defined grating period. A subsequent wet etch process located over the Bragg grating opens a sensing window in the device and reveals the grating structure.

High conversion efficiency single-pass second harmonic generation in a zinc-diffused periodically poled lithium niobate waveguide.

We report a modified technique for the fabrication of zinc-diffused channel waveguides using z-cut electric-field periodically poled LiNbO3. Unlike previous work, the diffusion was carried out using metallic zinc at atmospheric pressure. By optimizing the thermal diffusion parameters, channel waveguides that preserve the existing periodically poled domain structures, support both TE and TM modes, and enhance photorefractive damage resistance were obtained.