Abstract: A spot-size converter for coupling light between first and second waveguides respectively supporting first and second propagation modes having substantially different dimensions is provided. The spot-size converter includes a lower and an upper waveguiding structure each characterized by an effective refractive index. The lower waveguiding structure is coupled to the first waveguide to receive light therefrom or transmit light thereto in the first propagation mode. The upper waveguiding structure is coupled to the second waveguide to transmit light thereto or receive light therefrom in the second propagation mode. The upper waveguiding structure includes a plurality of longitudinally extending high-index elements arranged in multiple vertically spaced rows.

Abstract: A polarization rotator assembly for rotating a polarization mode of an electromagnetic signal is provided. The polarization rotator assembly has a waveguiding structure of co-extensive first and second layers defining, successively, an input portion, a subwavelength composite portion and a polarization rotating portion. The subwavelength composite portion is formed by the first and second layers, where the second layer defines a subwavelength pattern. The polarization rotator portion is geometrically configured to rotate the polarization mode of the electromagnetic signal.

Abstract: A polarization-insensitive optical receiver for demodulating a phase-modulated input optical signal is provided. The optical receiver includes successively a polarization splitter, a first and second interferometric modules including respective delay lines, and a plurality of detectors. The input optical signal is split into two substantially orthogonally-polarized components, which are launched along respective optical paths into the corresponding interferometric modules where they demodulated and subsequently recombined prior to being detected by the plurality of detectors. Advantageously, the optical receiver allows mitigating undesired discrepancies between the optical paths traveled by the two polarization components by arranging the respective delay lines of the interferometric modules into intertwined spiraling structures.

Abstract: A polarization rotator assembly for rotating a polarization mode of an electromagnetic signal is provided. The polarization rotator assembly has a waveguiding structure of co-extensive first and second layers defining, successively, an input portion, a subwavelength composite portion and a polarization rotating portion. The subwavelength composite portion is formed by the first and second layers, where the second layer defines a subwavelength pattern. The polarization rotator portion is geometrically configured to rotate the polarization mode of the electromagnetic signal.

Abstract: An optical coupling assembly for coupling light from an optical fiber including an angled tip into a planar waveguide via a waveguide coupling element is provided. In one embodiment, the optical fiber extends along the planar waveguide with the angled tip positioned such that light propagating in the optical fiber is coupled by the waveguide coupling element to propagate in the planar waveguide in counter propagation with respect to a fiber propagation direction. In another embodiment, the optical fiber includes a tapered peripheral portion tapering toward the angled tip and is disposed over the planar waveguide with the tapered peripheral portion extending therealong such that light propagating in the optical fiber is coupled to propagate in the planar waveguide with either forward or counter propagation. Embodiments of the present invention may be part of various photonic integrated circuits and may be manufactured more easily than known optical coupling assemblies.

Abstract: A low white frequency noise tunable semiconductor laser source is presented. The laser source includes a single-mode semiconductor laser assembly which generates a laser beam having a tunable frequency over a spectral range of interest. An optical filter is provided in the path of the laser beam. The optical filter has multiple spectral features distributed over the entire spectral range of interest. Each spectral feature has a narrow spectral range. A locking mechanism is further provided and is controllable for locking a spectral alignment between the frequency of the laser beam and any selected one of the spectral features of the optical filter.

Abstract: A method is provided for measuring a factor, called herein the single-port rejection ratio (SPRR), characterizing a balanced detection device. The SPRR is representative of the ratio of the weak differential output current measured under illumination of a single-port of the balanced detection device to the strong measurable differential output current obtained under dual-port illumination. An apparatus for measuring the SPRR is also provided.

Abstract: An optical coupling assembly for coupling light from an optical fiber including an angled tip into a planar waveguide via a waveguide coupling element is provided. In one embodiment, the optical fiber extends along the planar waveguide with the angled tip positioned such that light propagating in the optical fiber is coupled by the waveguide coupling element to propagate in the planar waveguide in counter propagation with respect to a fiber propagation direction. In another embodiment, the optical fiber includes a tapered peripheral portion tapering toward the angled tip and is disposed over the planar waveguide with the tapered peripheral portion extending therealong such that light propagating in the optical fiber is coupled to propagate in the planar waveguide with either forward or counter propagation. Embodiments of the present invention may be part of various photonic integrated circuits and may be manufactured more easily than known optical coupling assemblies.

Abstract: A low white frequency noise tunable semiconductor laser source is presented. The laser source includes a single-mode semiconductor laser assembly which generates a laser beam having a tunable frequency over a spectral range of interest. An optical filter is provided in the path of the laser beam. The optical filter has multiple spectral features distributed over the entire spectral range of interest. Each spectral feature has a narrow spectral range. A locking mechanism is further provided and is controllable for locking a spectral alignment between the frequency of the laser beam and any selected one of the spectral features of the optical filter.

Abstract: A method is provided for measuring a factor, called herein the single-port rejection ratio (SPRR), characterizing a balanced detection device. The SPRR is representative of the ratio of the weak differential output current measured under illumination of a single-port of the balanced detection device to the strong measurable differential output current obtained under dual-port illumination. An apparatus for measuring the SPRR is also provided.

Abstract: A method for designing an index profile suitable for encoding into a phase mask for manufacturing a complex optical grating is provided. The optical grating corresponds to a target index profile defining a target spectral response. A modified index profile is set equal to the target index profile and expressed as a function of an apodization and phase profiles. The modified index profile is iteratively further modified in order to provide the index profile suitable for encoding in the phase mask. This process creates side bands outside of a spectral region of interest, while maintaining the target spectral response within the spectral region of interest.

Abstract: A method for manufacturing a complex multi-channel optical grating using a phase mask is presented. A plurality of sub-gratings is designed, each having an individual spectral response designed to produce one of the channels of the multi-channel grating. The target profile of the grating is determined based on the combination of the index profiles of the individual sub-gratings, the target index profile defining a target spectral response of the multi-channel grating. A modified index profile having a smooth apodization profile but providing the same spectral response as the target index profile, at least within a spectral region of interest, is determined and encoded into the phase mask. The phase mask is then used to photoinduce the grating in a photosensitive medium.

Abstract: Methods to improve the optical properties of Bragg gratings are disclosed. A first method includes a post correction of the refractive index profile by applying an average index correction thereto. The average index correction is obtained through an analysis of the defects of the refractive index profile characterised through a reconstruction thereof. A second method includes a pre-correction to the refractive index profile by characterising the defects of a test grating, and again calculating an average index correction based thereon. Further gratings are then made using a corrected refractive index profile.

Abstract: A tunable optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components to the required values.

Abstract: A tunable dispersion compensator for the compensation of the chromatic dispersion experienced by a single-channel or multi-channel light signal. The compensator includes a plurality of optical structures such as chirped Bragg gratings or combinations thereof, each having a characteristic dispersion profile. An optical coupling arrangement successively propagates the light signal in each of these structures, so that it accumulates the dispersion compensation effect of each. A tuning device jointly tunes the dispersion profile of each optical structure by applying a same tuning force thereto, preferably a temperature gradient.

Abstract: A dispersion compensator for the compensation of chromatic dispersion in a multi-channel light signal is provided. The compensator includes a pair of optical structures each having a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. An optical assembly propagates the light signal sequentially through both optical structures. The periods of the grating components are selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components of each optical structures, and proper selection of the tuning parameters allows tuning independently both the dispersion and dispersion slope.

Abstract: An optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particluar channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal.

Abstract: Methods to improve the optical properties of Bragg gratings are disclosed. A first method includes a post correction of the refractive index profile by applying an average index correction thereto. The average index correction is obtained through an analysis of the defects of the refractive index profile characterised through a reconstruction thereof. A second method includes a pre-correction to the refractive index profile by characterising the defects of a test grating, and again calculating an average index correction based thereon. Further gratings are then made using a corrected refractive index profile.

Abstract: A tunable dispersion compensator for the compensation of the chromatic dispersion experienced by a single-channel or multi-channel light signal. The compensator includes a plurality of optical structures such as chirped Bragg gratings or combinations thereof, each having a characteristic dispersion profile. An optical coupling arrangement successively propagates the light signal in each of these structures, so that it accumulates the dispersion compensation effect of each. A tuning device jointly tunes the dispersion profile of each optical structure by applying a same tuning force thereto, preferably a temperature gradient.

Abstract: An optical imaging system for detecting light from an excitation light source through a scattering medium. The system includes a photo detector for receiving light from the scattering medium, an amplification circuit coupled from the photo-detector, an electro-optical source coupled from the amplification circuit for providing a secondary light signal, and a streak camera receiving the secondary light signal and providing an image of the scattering medium.