Abstract: A method and apparatus is provided for determining the thickness of coating layers of a curved surface when examining the surface with terahertz radiation. The method involves measuring detected reflected radiation and applies a correction factor to obtain the thicknesses of the layers. This addresses the problem of compensating for the curvature of the surface when determining coating thickness.

Abstract: A range of technique for investigating a sample such as obtaining images and/or spectral information are described. The techniques include a method for deriving structural information about a sample as a continuous function of the depth below the surface of the sample, a method for evaluating a part of the structure of a sample located between two interfaces within the sample, and a contrast enhancing method and apparatus which has a quick image acquisition time.

Abstract: A probe assembly for examining a sample, the assembly including a probe, a fiber optic cable for communicating signals to and/or from the probe, an emitter for emitting radiation to irradiate the sample and an electro-magnetic radiation detector for detecting radiation which is transmitted or reflected from the sample. The emitter includes a frequency conversion member which emits radiation in response to being irradiated with input radiation which has a different frequency to that of the emitted radiation. At least one of the emitter or detector is located in the probe. The probe is particularly for use as an endoscope or for imaging teeth. The invention also extends to a method of imaging teeth, and apparatus for imaging diseased teeth, for example, teeth with caries or suffering from periodontal disease.

Abstract: A method configured to investigate an LCD structure, the method comprising: irradiating an LCD structure with pulsed radiation having at least one frequency in the range from 40G Hz to 100 THz; detecting radiation which has been transmitted through or reflected by the structure; determining information about the structure by measuring a quantity at least related to the amplitude of the detected radiation.

Abstract: A method of imaging a sample, the method comprising: (a) irradiating a sample with a pulse of electromagnetic radiation, said pulse having a plurality of frequencies in the range from 25 GHz to 100 THz; (b) determining a first parameter related to the amplitude of the radiation, which is either reflected from and/or transmitted by the sample, in the time domain; (c) calculating the value of the first parameter at a first time value relative to the value of the first parameter at a second time value which coincides with a physical feature of the dataset of the first parameter with respect to time; and (d) generating an image by plotting the value calculated in step (c) for different points of the sample.

Abstract: A method for investigating the macromolecular structure of a molecular sample, the method composing irradiating the sample with radiation having a plurality of frequencies in the range of 25 GHz to 20 THz; detecting radiation reflected from and/or transmitted by said sample to obtain a spectra of the sample; and identifying structure in the resultant spectra which arises from intermolecular interactions.

Abstract: An apparatus for investigating a sample comprising a source of a beam of radiation, a detector for detecting a beam of radiation reflected by or transmitted through a sample to be imaged, an optical subsystem for manipulating the beam between the source and detector and means for translating the optical subsystem along a first translation axis relative to the source and detector to scan the beam across the sample, wherein the source and the detector are on opposite sides of the subsystem and the beam from the source and the beam reflected or transmitted each enter and exit the subsystem in a direction parallel to the first direction of translation. The apparatus is also suitable for maintaining the relative phase of two beams of radiation, during translation of an optical subsystem.

Abstract: An apparatus and method for imaging a sample, the apparatus including a source for irradiating a sample with a beam of substantially continuous electromagnetic radiation having a frequency in the range 25 GHz to 100 THz; means for subdividing an area of the sample which is to be imaged into a two dimensional array of pixels; means for detecting radiation from each pixel wherein the detector is configured to detect a phase dependent quantity of the detected radiation which is measured relative to the radiation which irradiates the sample.

Abstract: A system for investigating a sample, the system including a detector having non-linear current voltage characteristics and being configured to mix two radiation signals having frequencies in the range from 25 GHz to 100 THz, one of the signals being a local oscillator signal and the other signal being a sample signal carrying information about the sample being investigated, the system further having a quantum cascade laser for providing at least the local oscillator signal.

Abstract: A radiation source comprising a frequency conversion member (1) configured to emit a beam of emitted radiation (7) with at least one frequency in the range from 0.1 THz to 100 THz, in response to irradiation with an input beam (3) with a frequency different to that of the emitted radiation (7), the source being subjected to a magnetic field (9) which has a component parallel to that of the emitted beam of radiation (7). The radiation source may be optimised by using both the fluence of the input beam and the magnetic field or may comprise a magnetically doped frequency conversion member or also have means for applying an electric field.

Abstract: In an apparatus and method for imaging a sample: a) the sample to be imaged is irradiated with pulsed electro-magnetic radiation with a plurality of frequencies in the range from 50 GHz to 84 THz; b) an area of the sample is subdivided into a two dimensional array of pixels, and radiation from each pixel is detected over a plurality of frequencies; and c) an image is generated from the radiation detected in step (b) preferably using a frequency or a selection of frequencies from the plurality of frequencies in the pulsed electro-magnetic radiation. The method can be used as a medical imaging technique and can be used to image cancer tumours.

Abstract: An apparatus for investigating a sample, the apparatus comprising an emitter (1) for irradiating the sample (27) with a beam of emitted electromagnetic radiation; and a detector (49) for detecting the radiation reflected from the sample, wherein there is an optically non-linear member (15) which functions as both an active part of the emitter and an active part of the detector, said emitter and detector using the same part of the optically non-linear member (15). The electromagnetic radiation is primarily intended to be in the terahertz (THz) frequency range.

Abstract: A method and apparatus for imaging a sample, the method comprising the steps of: a) irradiating a sample to be imaged with a beam of pulsed electromagnetic radiation with a plurality of frequencies in the range from 25 GHz to 100 THz; b) detecting radiation which is both transmitted through and reflected from the sample; and c) generating an image of the sample from radiation detected in step (b). The method and apparatus can be used to generate a three-dimensional image of the sample and/or a compositional image of the sample.

Abstract: A system for investigating a sample, the system comprising a detector having non-linear current voltage characteristics and being configured to mix two radiation signals having frequencies in the range from 25 GHz to 100 THz, one of the signals being a local oscillator signal and the other signal being a sample signal carrying information about the sample being investigated, the system further comprising a quantum cascade laser for providing at least the local oscillator signal.

Abstract: An apparatus for investigating a sample comprising a source of a beam of radiation, a detector for detecting a beam of radiation reflected by or transmitted through a sample to be imaged, an optical subsystem for manipulating the beam between the source and detector and means for translating the optical subsystem along a first translation axis relative to the source and detector to scan the beam across the sample, wherein the source and the detector are on opposite sides of the subsystem and the beam from the source and the beam reflected or transmitted each enter and exit the subsystem in a direction parallel to the first direction of translation. The apparatus is also suitable for maintaining the relative phase of two beams of radiation, during translation of an optical subsystem.

Abstract: An apparatus and method for imaging a sample, the apparatus comprising: a source for irradiating a sample with a beam of substantially continuous electromagnetic radiation having a frequency in the range 25 GHz to 100 THz; means for subdividing an area of the sample which is to be imaged into a two dimensional array of pixels; means for detecting radiation from each pixel wherein the detector is configured to detect a phase dependent quantity of the detected radiation which is measured relative to the radiation which irradiates the sample.

Abstract: An apparatus for investigating a sample, the apparatus comprising an emitter (1) for irradiating the sample (27) with a beam of emitted electromagnetic radiation; and a detector (49) for detecting the radiation reflected from the sample, wherein there is an optically non-linear member (15) which functions as both an active part of the emitter and an active part of the detector, said emitter and detector using the same part of the optically non-linear member (15). The electromagnetic radiation is primarily intended to be in the terahertz (THz) frequency range.

Abstract: An apparatus and method for investigating a sample, the apparatus comprising: means (61) for irradiating the sample (21) with a first beam of electromagnetic radiation configured to excite an optically non-linear process within the sample; means (61) for irradiating the sample with a second beam of electromagnetic radiation; and a detector (41) for detecting a change the second beam after it has been reflected from or transmitted through the sample. If the optically non-linear process is a second order process, the detector could be used to detect a change in the polarisation of the second beam. Apparatus and method find application of samples with terahertz (THZ) radiation locally generated and detected within the sample.

Abstract: A range of technique for investigating a sample such as obtaining images and/or spectral information are described. The techniques include a method for deriving structural information about a sample as a continuous function of the depth below the surface of the sample, a method for evaluating a part of the structure of a sample located between two interfaces within the sample, and a contrast enhancing method and apparatus which has a quick image acquisition time.

Abstract: An optical device for efficient radiation emission having a modulation region with phase matching means (1) for enhancing the phase matching between two different frequency signals propagating in the optical modulation region (1) in response to illumination by at least one incident beam (7, 8), the phase matching means (1), having a spatial variation in its refractive index (5) along the path of the incident radiation beam (7, 8). The device may be configured as a radiation source comprising a frequency conversion member (C2) for emitting a beam of radiation (553) in response to irradiation by one or more input beams (507), the emitted beam (553) having a frequency different to that of the one or more input beams (507), the one or more input beams (507) all being produced within a lasing cavity (defined by M3, M4, M5, M6 and output coupler (523)) and said frequency conversion member (C2) being located within said lasing cavity. The invention also extends to an imaging system using the radiation source.