[Show abstract][Hide abstract] ABSTRACT: Large-scale integrated quantum photonic technologies will require on-chip integration of identical photon sources with reconfigurable waveguide circuits. Relatively complex quantum circuits have been demonstrated already, but few studies acknowledge the pressing need to integrate photon sources and waveguide circuits together on-chip. A key step towards such large-scale quantum technologies is the integration of just two individual photon sources within a waveguide circuit, and the demonstration of high-visibility quantum interference between them. Here, we report a silicon-on-insulator device that combines two four-wave mixing sources in an interferometer with a reconfigurable phase shifter. We configured the device to create and manipulate two-colour (non-degenerate) or same-colour (degenerate) path-entangled or path-unentangled photon pairs. We observed up to 100.0 +/- 0.4% visibility quantum interference on-chip, and up to 95 +/- 4% off-chip. Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits and is a first step towards fully integrated quantum technologies.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate three and four input multiports in a three dimensional glass platform, fabricated using the femtosecond laser direct-write technique. Hong-Ou-Mandel (HOM) interference is observed and a full quantum characterization is performed, obtaining two photon correlation matrices for all combinations of input and output ports. For the 3-port case, the quantum visibilities are accurately predicted solely from measurement of the classical coupling ratios.
[Show abstract][Hide abstract] ABSTRACT: In the two decades since the first extra-solar planet was discovered, the
detection and characterization of extra-solar planets has become one of the key
endeavors in all of modern science. Recently direct detection techniques such
as interferometry or coronography have received growing attention because they
reveal the population of exoplanets inaccessible to Doppler or transit
techniques, and moreover they allow the faint signal from the planet itself to
be investigated. Next-generation stellar interferometers are increasingly
incorporating photonic technologies due to the increase in fidelity of the data
generated. Here, we report the design, construction and commissioning of a new
high contrast imager; the integrated pupil-remapping interferometer; an
instrument we expect will find application in the detection of young faint
companions in the nearest star-forming regions. The laboratory characterisation
of the instrument demonstrated high visibility fringes on all interferometer
baselines in addition to stable closure phase signals. We also report the first
successful on-sky experiments with the prototype instrument at the 3.9-m
Anglo-Australian Telescope. Performance metrics recovered were consistent with
ideal device behaviour after accounting for expected levels of decoherence and
signal loss from the uncompensated seeing. The prospect of complete
Fourier-coverage coupled with the current performance metrics means that this
photonically-enhanced instrument is well positioned to contribute to the
science of high contrast companions.
Monthly Notices of the Royal Astronomical Society 10/2012; 427(1). · 5.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Highly localized fiber Bragg gratings can be inscribed point-by-point with focused ultrashort pulses. The transverse localization of the resonant grating causes strong coupling to cladding modes of high azimuthal and radial order. In this paper, we show how the reflected cladding modes can be fully analyzed, taking their vectorial nature, orientation and degeneracies into account. The observed modes' polarization and intensity distributions are directly tied to the dispersive properties and show abrupt transitions in nature, strongly correlated with changes in the coupling strengths.
[Show abstract][Hide abstract] ABSTRACT: We present an experimental and theoretical analysis of the influence of scattering losses on the net reflectivity of fiber Bragg gratings inscribed with a femtosecond laser and the point-by-point technique. We demonstrate that the ratio of the coupling strength coefficient to the scattering loss coefficient varies significantly with the inscribing laser pulse energy, and highlight that an optimal pulse-energy range exists for achieving high-reflectivity gratings. These results are critical for exploiting high power fiber laser opportunities based on point-by-point gratings.
[Show abstract][Hide abstract] ABSTRACT: We report the performance of a dual-wavelength waveguide laser based on a phase-modulated sampled-grating architecture fabricated using the femtosecond laser direct-write technique. The waveguide laser was written in Yb-doped phosphate glass and had a narrow linewidth (<10 pm), high signal-to-noise ratio (>60 dB), 5 mW output power per channel, and wavelength separation of 10 nm.
[Show abstract][Hide abstract] ABSTRACT: We report the generation of correlated photon pairs in the telecom C-band at room temperature from a dispersion-engineered silicon photonic crystal waveguide. The spontaneous four-wave mixing process producing the photon pairs is enhanced by slow-light propagation enabling an active device length of less than 100 μm. With a coincidence to accidental ratio of 12.8 at a pair generation rate of 0.006 per pulse, this ultracompact photon pair source paves the way toward scalable quantum information processing realized on-chip.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate apodized fiber Bragg gratings (FBGs) inscribed with a point-by-point (PbP) technique. We tailor the grating phase and coupling amplitude through precise control over the longitudinal and transverse positions of each laser-inscribed modification. This method of apodization is facilitated by the highly localized, high-contrast modifications generated by focused IR femtosecond laser inscription. Our technique provides a simple method for the design and implementation of PbP FBGs with complex apodization profiles.
[Show abstract][Hide abstract] ABSTRACT: We report on dual wavelength DFB waveguide lasers near 1030nm in Yb phosphate glass incorporating fs-written point by point sampled Bragg gratings and in single line mode operation ranging from 985nm to 1085nm.
[Show abstract][Hide abstract] ABSTRACT: We present a narrow-linewidth, linearly polarized neodymium-doped fiber laser that incorporates a point-by-point Bragg grating inscribed into the core of a single-polarization all-solid photonic bandgap fiber. The Bragg grating was written within a single-polarization wavelength band of the fiber; thus, the Bragg reflection was polarized. This all-fiber laser produced 7.2 W, linearly polarized output with 25 pm FWHM and 19.6 dB polarization extinction ratio.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate the fabrication by direct laser writing and the operation of a directional coupler containing Bragg gratings in each waveguide. We achieve high-precision control over the longitudinal shift between the gratings, which feature first-order Bragg resonance at telecommunication wavelengths. We observe fundamental differences between light transmission characteristics in couplers with unshifted and shifted gratings in agreement with theoretical predictions.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate photon-pair generation in a reverse proton exchanged waveguide
fabricated on a periodically poled magnesium doped stoichiometric lithium
tantalate substrate. Detected pairs are generated via a cascaded second order
nonlinear process where a pump laser at wavelength of 1.55 $\mu$m is first
doubled in frequency by second harmonic generation and subsequently
downconverted around the same spectral region. Pairs are detected at a rate of
42 per second with a coincidence to accidental ratio of 0.7. This cascaded pair
generation process is similar to four-wave-mixing where two pump photons
annihilate and create a correlated photon pair.
[Show abstract][Hide abstract] ABSTRACT: Integrated optics provides an ideal test bed for the emulation of quantum
systems via continuous-time quantum walks. Here we study the evolution of
two-photon states in an elliptic array of waveguides. We characterise the
photonic chip via coherent-light tomography and use the results to predict
distinct differences between temporally indistinguishable and distinguishable
two-photon inputs which we then compare with experimental observations. Our
work highlights the feasibility for emulation of coherent quantum phenomena in
three-dimensional waveguide structures.
New Journal of Physics 03/2011; 13(7). · 4.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Third-harmonic generation microscopy has been used to analyze the morphology of photonic structures created using the femtosecond laser direct-write technique. Three-dimensional waveguide arrays and waveguide-Bragg gratings written in fused-silica and doped phosphate glass were investigated. A sensorless adaptive-optical system was used to correct the optical aberrations occurring in the sample and microscope system, which had a lateral resolution of less than 500 nm. This nondestructive testing method creates volume reconstructions of photonic devices and reveals details invisible to other linear microscopy and index profilometry techniques.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate Point-by-Point Bragg grating inscription into the core of a single-polarisation all-solid photonic bandgap fibre. Grating strength of 7.5 dB (>;80% reflectivity) was realised at 1064 nm with linearly-polarised feedback.
Optical Fibre Technology (ACOFT), 2010 35th Australian Conference on; 01/2011
[Show abstract][Hide abstract] ABSTRACT: The spectral characteristics of a fiber Bragg grating (FBG) with a transversely inhomogeneous refractive index profile, differs considerably from that of a transversely uniform one. Transmission spectra of inhomogeneous and asymmetric FBGs that have been inscribed with focused ultrashort pulses with the so-called point-by-point technique are investigated. The cladding mode resonances of such FBGs can span a full octave in the spectrum and are very pronounced (deeper than 20dB). Using a coupled-mode approach, we compute the strength of resonant coupling and find that coupling into cladding modes of higher azimuthal order is very sensitive to the position of the modification in the core. Exploiting these properties allows precise control of such reflections and may lead to many new sensing applications.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate the first 1550 nm correlated photon-pair source in a highly nonlinear integrated glass waveguide. A pair coincidence rate of 80 s(-1) was achieved with the correlation ratio limited by Raman effects. (C) 2011 Optical Society of America
[Show abstract][Hide abstract] ABSTRACT: Interferometry using photonic pupil remapping holds great promise in stellar astronomy and in the detection of exoplanets. However the development of this novel technique has revealed new challenges in the use of photonic devices.
[Show abstract][Hide abstract] ABSTRACT: form only given. Aperture masking has gained widespread use within the optical stellar interferometry community as a way of obtaining high fidelity imaging data on various classes of stellar targets. Aperture masking involves apodizing the starlight at the pupil plane of a telescope, typically using a plate with many small sub-apertures, and then recombining the beams in a Fizeau interferometric scheme at the detector/camera. By appropriate analysis of the spatial interference pattern, it is possible to reconstruct an image with high fidelity. This has proven to be an extremely successful technique when imaging from ground-based telescopes as structures within the immediate vicinity of the diffraction-limited core are extremely difficult to recover with competing methods. Recent reformulations of this basic idea propose replacing the mask with a number of single-mode optical waveguides which sample the pupil plane. Waveguides offer several advantages. Firstly, the light within a single-mode guide propagates with planar wavefronts. As a result, the phase is flat across each sub-aperture, which is important for precise calibration of the interference pattern. Secondly, waveguides can be routed from a 2D input plane to ID output plane (known as pupil remapping) so that interferometry can be performed on an integrated chip (via couplers). An ideal technology for achieving the reformatting in 3D is the laser direct write technique. Finally, waveguides allow a redundant 2D array of sub-apertures to be made non-redundant at the output. This means that all of the light in the pupil plane can be utilised (by contrast, an aperture mask may discard more than 95% of the starlight), hence higher throughputs can be achieved. We discuss the design, fabrication and performance of a pupil remapping system consisting of a 2D to ID (femtosecond laser written) chip with 8 single mode waveguides designed to operate at 1550 nm (C-band or H band) over a bandwidth of ~300 nm, a mic- - ro-lens array and computer controlled segmented mirror (MEMS). The combination of a micro-lens array and MEMS were used to maximise or minimise the coupling into the pupil remapping chip so as to be able to switch between particular baselines and hence simulate a non-redundant output distribution. We demonstrate relatively high throughputs, 55-65% across all guides and minimal cross coupling between any two guides (