The invention provides methods and apparatus comprising a multi-wavelength laser source that uses a single unfocused pulse of a low intensity but high power laser over a large sample area to collect Raman scattered collimated light, which is then Rayleigh filtered and focused using a singlet lens into a stacked fiber bundle connected to a customized spectrograph, which separates the individual spectra from the scattered wavelengths using a hybrid diffraction grating for collection onto spectra-specific sections of an array photodetector to measure spectral intensity and thereby identify one or more compounds in the sample.

In an example, an Echelle grating wavelength division multiplexing (WDM) device includes a first waveguide, a slab waveguide, multiple second waveguides, an Echelle grating, and a metal-filled trench. The first waveguide includes either an input waveguide or an output waveguide. The multiple second waveguides are optically coupled to the first waveguide through the slab waveguide. The multiple second waveguides include multiple output waveguides if the first waveguide includes the input waveguide or multiple input waveguides if the first waveguide includes the output waveguide. The Echelle grating includes multiple grating teeth formed in the slab waveguide. The metal-filled trench forms a mirror at the grating teeth to reflect incident light from the first waveguide toward the multiple second waveguides or from the multiple second waveguides toward the first waveguide.

There is provided an optical measurement method using a detector having a detection sensitivity to at least a near-infrared region. The optical measurement method including: obtaining an output value by measuring a light sample at any exposure time with the detector; and correcting the output value with an amount of correction corresponding to the output value, when the exposure time at which the output value is obtained is within a second range. The amount of correction includes a product of a coefficient and a square of the exposure time, the coefficient indicating a degree to which an output value obtained when the light sample is measured with the detector at an exposure time within the second range deviates from output linearity obtained when the light sample is measured with the detector at an exposure time within a first range.

Apparatus for measuring spectra from one or more samples, the apparatus including a reference waveguide that receives illuminating radiation used to illuminate at least one sample, at least one sample waveguide that receives sample radiation at least one of reflected from and transmitted through a respective sample, an optical system that spatially distributes radiation from each of the waveguides based on a frequency of the radiation, and focuses radiation from the optical fibres into an imaging plane and an imaging device that captures an image of the focused and spatially distributed radiation from the imaging plane so that the image includes respective spectra from each of the waveguides.

Spectrographic measurements are often limited by the amount of light that is available. Photons that are not collected or measured reduce the signal to noise and therefore reduce measurement precision. This invention collects the zero order light and sends it through the spectrometer again. In an atmospheric LIDAR, the zero order recycling is estimated to increase the rotational Raman signal by an additional 20%. A grating based spectrometer where the zero order light is collected by a lens or mirror and focused into a fiber optic that sends the light to the input slit where it is directed into the spectrometer again. There can be a plurality of recycle fibers. The detector can be either a single linear array or a two dimensional array such as a CCD or CMOS camera.

A hyperspectral imaging system and method are described herein for providing a hyperspectral image of an area of a remote object. In one embodiment, the hyperspectral imaging system includes an optic, a stack of waveguide plates, a spectral filter array, a detector array, and a controller.

In an example, an Echelle grating wavelength division multiplexing (WDM) device includes a first waveguide, a slab waveguide, multiple second waveguides, an Echelle grating, and a metal-filled trench. The first waveguide includes either an input waveguide or an output waveguide. The multiple second waveguides are optically coupled to the first waveguide through the slab waveguide. The multiple second waveguides include multiple output waveguides if the first waveguide includes the input waveguide or multiple input waveguides if the first waveguide includes the output waveguide. The Echelle grating includes multiple grating teeth formed in the slab waveguide. The metal-filled trench forms a mirror at the grating teeth to reflect incident light from the first waveguide toward the multiple second waveguides or from the multiple second waveguides toward the first waveguide.

A single strand of an optical fiber with a single optical core that is dimensioned at one end to resemble a blade or a head of a flat-head screwdriver. Such strand of the optical fiber is configured for optical coupling of light between such single strand and a spectrometric/spectrophotometric apparatus while employing an input slit and/or an output slit of the apparatus. A method for fabricating such single strand. A fiber optic cable containing, as an optical medium, only such single strand. A method for handling light with the use of such optical fiber and/or the optical cable.

A photonic crystal waveguide for conveying light with an input end and an output end to supply for an electromagnetic spectrometer includes: an input end having a convex envelope of a cross-section of the waveguide at the input end, which envelope defines a circular shape or a shape of a regular polygon with n1 corners, wherein n1 is a natural number bigger than 3; an output end having a cross-section that defines a slit shape; and a plurality of photonic crystal fibers, wherein an arrangement of the plurality of photonic crystal fibers defines the cross-sections at the input and output ends.

Apparatus for hyperspectral imaging, the apparatus including input optics that receive radiation reflected or radiated from a scene, a spatial modulator that spatially samples radiation received from the input optics to generate spatially sampled radiation, a spectral modulator that spectrally samples the spatially sampled radiation received from the spatial modulator to generate spectrally sampled radiation, a sensor that senses spectrally sampled radiation received from the spectral modulator and generates a corresponding output signal and at least one electronic processing device that controls the spatial and spectral modulators to cause spatial and spectral sampling to be performed, receives output signals and processes the output signals in accordance with performed spatial and spectral sampling to generate a hyperspectral image.