Optical device and imaging system

An optical device comprising:

• an optical modulation region which comprises phase matching means for enhancing the phase matching between at least two different frequency signals propagating in the optical modulation region in response to illumination by at least one incident beam of radiation, the phase matching means having a spatial variation in its refractive index along a component of the incident radiation beam configured to maximise a distance in the modulation region over which the at least two different frequency signals stay in phase,
• the modulation region further comprising frequency conversion means for emitting a beam with an emitted radiation frequency in response to illumination by the at least one input beam, the emitted beam having a different frequency to that of the or an incident beam;
• the phase matching means enhancing the phase matching between the polarisation generated by the or an incident beam and the emitted beam.

A radiation source comprising:

• a frequency conversion member for emitting a beam of radiation in response to irradiation by a pulsed input beam having a plurality of frequency components, the emitted beam having a frequency different to that of the frequency components of the pulsed input beam,
• the pulsed input beam being produced within a lasing cavity and said frequency conversion member being located within said lasing cavity.

A radiation source comprising:

• a frequency conversion member for emitting a beam of radiation in response to irradiation by one or more input beams, the emitted beam having a frequency substantially equal to the difference between two frequency components of the one or more input beams, the one or more input beams all being produced within a lasing cavity and said frequency conversion member being located within said cavity.

An imaging system comprising a radiation source for supplying a beam of imaging radiation onto an object and a detector, the radiation source comprising

• a frequency conversion member for emitting a beam of radiation in response to irradiation by a pulsed input beam having a plurality of frequency components, the emitted beam having a frequency different to that of the components of the pulsed input beam,
• the pulsed input beam being produced within a lasting cavity and said frequency conversion member being located within said lasing cavity.

An imaging system comprising a radiation source for supplying a beam of imaging radiation onto an object and a detector, the radiation source comprising

• a frequency conversion member for emitting a beam of radiation in response to irradiation by one or more input beams, the emitted beam having a frequency different to that of the one or more input beams,
• the one or more input beams all being produced within a lasing cavity and said frequency conversion member being located within said lasing cavity,
• the detector comprising a non-linear crystal, wherein said imaging radiation is detected by the non-linear crystal using a reference beam with a different wavelength to that emitted by the frequency conversion member.

A radiation source comprising:

• a frequency conversion member for emitting a beam of radiation in response to irradiation by one or more input beams, the emitted beam having a frequency different to that of the one or more input beams,
• the one or more input beams all being produced within a lasing cavity and said frequency conversion member being located within said lasing cavity,
• the source further comprising an output coupler which is capable of transmitting the emitted beam and reflecting the input beam or beams.