Techniques are provided for implementing a low insertion loss optical coupler utilizing a low confinement planar optical waveguide and two high confinement planar optical waveguides. The optical coupler efficiently couples an optical signal with a cross section greater than either high confinement planar optical waveguide.

A radiation carrier for carrying at least a radiation beam has, on a surface thereof, at least one excitation grating, for directing at least an excitation radiation beam directionally out of the radiation carrier, thereby illuminating a region of interest; and at least one structure for redirecting emission radiation emanating from the region of interest. Further a sensor is provided comprising at least one such radiation carrier and at least one detector, the structure being adapted for redirecting radiation from the region of interest into the at least one detector.

A radiation carrier for carrying at least a radiation beam has, on a surface thereof, at least one excitation grating, for directing at least an excitation radiation beam directionally out of the radiation carrier, thereby illuminating a region of interest; and at least one structure for redirecting emission radiation emanating from the region of interest. Further a sensor is provided comprising at least one such radiation carrier and at least one detector, the structure being adapted for redirecting radiation from the region of interest into the at least one detector.

In one embodiment of the disclosure, it is proposed diffraction grating structure comprising several grating lines. The diffraction grating structure is associated with a propagation layer, and the diffraction grating structure is made of a material that has a refractive index being equal to n.sub.2 (). The diffraction grating structure is remarkable in that it comprises 1/T grating lines per m, with T=(n.sub.2 ()+1)/, where is a wavelength defined from an incident electromagnetic wave.

Provided is an optical waveguide with an inscribed Bragg grating, where the Bragg grating is stable at high temperature, has low scattering loss and high reflectivity. Also provided is a method for inscribing a Bragg grating in an optical waveguide, the method comprising irradiating the optical waveguide with electromagnetic radiation from an ultrashort pulse duration laser of sufficient intensity to cause a permanent change in an index of refraction within a core of the optical waveguide, where the irradiating step is terminated prior to erasure of a Bragg resonance, and heating the optical waveguide to a temperature and for a duration sufficient to substantially remove a non-permanent grating formed in the optical waveguide by the irradiating step.

Provided is an optical waveguide with an inscribed Bragg grating, where the Bragg grating is stable at high temperature, has low scattering loss and high reflectivity. Also provided is a method for inscribing a Bragg grating in an optical waveguide, the method comprising irradiating the optical waveguide with electromagnetic radiation from an ultrashort pulse duration laser of sufficient intensity to cause a permanent change in an index of refraction within a core of the optical waveguide, where the irradiating step is terminated prior to erasure of a Bragg resonance, and heating the optical waveguide to a temperature and for a duration sufficient to substantially remove a non-permanent grating formed in the optical waveguide by the irradiating step.

An integrated wavelength-selective filter device comprises a first optical element, for directing received radiation into a direction defined by a first angle, and a second optical element being a diffractive element configured for diffracting the directed radiation under a second angle. The second angle is such that for a single reference wavelength the diffracted radiation is directed into a propagation medium for advancing therein towards a predetermined position on the first optical element or on a further optical element for filtering radiation having a wavelength substantially matching the reference wavelength from radiation having a substantially different wavelength. The propagation medium is formed from a material that is different from any material of the substrate of the first and the second optical element.

An integrated wavelength-selective filter device comprises a first optical element, for directing received radiation into a direction defined by a first angle, and a second optical element being a diffractive element configured for diffracting the directed radiation under a second angle. The second angle is such that for a single reference wavelength the diffracted radiation is directed into a propagation medium for advancing therein towards a predetermined position on the first optical element or on a further optical element for filtering radiation having a wavelength substantially matching the reference wavelength from radiation having a substantially different wavelength. The propagation medium is formed from a material that is different from any material of the substrate of the first and the second optical element.

An optical waveguide 15 includes a substrate 19, a core layer 12, a support 20, and a suppressing portion. The core layer 12 includes a light propagating portion 10 and a diffraction grating portion 11. The diffraction grating portion 11 includes a fine line pattern formed therein. The support 20 is made from a material having a smaller refractive index than a refractive index of the core layer 12. The support 20 supports the core layer 12 with respect to the substrate 19. The suppressing portion suppresses deformation of fine lines 13 that form the fine line pattern. The support 20 is not provided in an entire region between the light propagating portion 10 and the substrate 19 in a cross-section perpendicular to a longitudinal direction of the core layer 12 at least at a position in the longitudinal direction.

An optical waveguide 15 includes a substrate 19, a core layer 12, a support 20, and a suppressing portion. The core layer 12 includes a light propagating portion 10 and a diffraction grating portion 11. The diffraction grating portion 11 includes a fine line pattern formed therein. The support 20 is made from a material having a smaller refractive index than a refractive index of the core layer 12. The support 20 supports the core layer 12 with respect to the substrate 19. The suppressing portion suppresses deformation of fine lines 13 that form the fine line pattern. The support 20 is not provided in an entire region between the light propagating portion 10 and the substrate 19 in a cross-section perpendicular to a longitudinal direction of the core layer 12 at least at a position in the longitudinal direction.