Method and apparatus for generating THz radiation

A method of generating THz radiation, comprising the steps of:

• generating optical input radiation with an input radiation source device, wherein the optical input radiation generated with the input radiation source device comprises a first radiation component including an optical frequency and a second radiation component including the THz frequency of the THz radiation to be generated,
• irradiating a first conversion crystal device with the optical input radiation, wherein the first conversion crystal device is arranged in a single pass configuration, wherein the first radiation component and the second radiation component irradiate the first conversion crystal device with a mutual spatial and temporal overlap along a beam path through the first conversion crystal device, and
• generating the THz radiation having a THz frequency in the first conversion crystal device in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device, wherein the multi-line frequency spectrum is provided by beating frequencies derived from the optical frequency of the first radiation component and the THz frequency of the second radiation component, and
• the optical-to-THz-conversion process includes cascaded difference frequency generation using the multi-line frequency spectrum.

A method of generating THz radiation, comprising the steps of:

• generating optical input radiation with an input radiation source device, wherein the optical input radiation generated with the input radiation source device comprises a sequence of optical laser pulses having a temporal separation (Δt) equal to an integer multiple of a reciprocal of the THz frequency of the THz radiation to be generated (Δt=N·1/fTHz, N=1, 2, . . . ),
• irradiating a first conversion crystal device with the optical input radiation, wherein the first conversion crystal device is arranged in a single pass configuration, and
• generating the THz radiation having a THz frequency in the first conversion crystal device in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device, wherein the multi-line frequency spectrum is directly provided by the optical input radiation, and
• the optical-to-THz-conversion process includes cascaded difference frequency generation using the multi-line frequency spectrum.

A method of generating THz radiation, comprising the steps of:

• generating optical input radiation with an input radiation source device,
• irradiating a first conversion crystal device with the optical input radiation, wherein the first conversion crystal device is arranged in a single pass configuration, and
• generating the THz radiation having a THz frequency in the first conversion crystal device in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device, and
• the optical-to-THz-conversion process includes cascaded difference frequency generation using the multi-line frequency spectrum, wherein the method further includes
• irradiating at least one further conversion crystal device arranged at an output side of the first conversion crystal device with at least one of the optical input radiation and the THz radiation, and
• generating THz radiation in the at least one further conversion crystal device in response to the optical input radiation by the optical-to-THz-conversion process.

A method of generating THz radiation, comprising the steps of:

• generating optical input radiation with an input radiation source device,
• irradiating a first conversion crystal device with the optical input radiation, wherein the first conversion crystal device is arranged in a single pass configuration, and
• generating the THz radiation having a THz, frequency in the first conversion crystal device in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device, and
• the optical-to-THz-conversion process includes cascaded difference frequency generation using the multi-line frequency spectrum, wherein
• each conversion crystal device is cooled with a cooling device.

A THz source apparatus, being configured for generating THz radiation, comprising

• an input radiation source device being arranged for generating optical input radiation, and
• a first conversion crystal device being arranged to be irradiated with the optical input radiation, wherein
• the first conversion crystal device is arranged in a single pass configuration and for generating the THz radiation having a THz frequency in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• the input radiation source device and the first conversion crystal device are configured such that a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device and the optical-to-THz-conversion process includes cascaded difference frequency generation of the optical input radiation using the multi-line frequency spectrum, wherein
• the input radiation source device is arranged for generating a first radiation component including an optical frequency and a second radiation component including an optical frequency separated from the first radiation component optical frequency by the TEL frequency of the THz radiation to be generated or including the THz frequency of the THz radiation to be generated, wherein the first radiation component and the second radiation component irradiate the first conversion crystal device with a mutual spatial and temporal overlap along a beam path through the first conversion crystal device, and
• the input radiation source device has two laser sources locked to each other and configured to generate the first radiation component and the second radiation component, respectively, the laser sources including
• two continuous wave laser sources,
• two quasi-continuous wave laser sources configured to emit pulses having a duration in a range from 100 ps to 10 ns,
• one continuous wave laser source and one quasi-continuous wave laser source,
• two pulse laser sources configured to emit pulses having a duration in a range from 10 fs to 100 ps,
• one broadband chirped puke laser source, combined with a pulse stretcher, and one pulse laser source, combined with a relative delay unit, or
• two broadband chirped pulse laser sources, combined with a relative delay unit.

A THz source apparatus, being configured for generating THz radiation, comprising

• an input radiation source device being arranged for generating optical input radiation, and
• a first conversion crystal device being arranged to be irradiated with the optical input radiation, wherein
• the first conversion crystal device is arranged in a single pass configuration and for generating the THz radiation having a THz frequency in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• the input radiation source device and the first conversion crystal device are configured such that a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device and the optical-to-THz-conversion process includes cascaded difference frequency generation of the optical input radiation using the multi-line frequency spectrum, wherein
• the input radiation source device is arranged for generating a sequence of optical laser pulses having a temporal separation (Δt) equal to an integer multiple of a reciprocal of the THz frequency of the THz radiation to be generated (Δt=N·1/fTHz, N=1, 2, . . . ).

A THz source apparatus, being configured for generating THz radiation, comprising

• an input radiation source device being arranged for generating optical input radiation, and
• a first conversion crystal device being arranged to be irradiated with the optical input radiation, wherein
• the first conversion crystal device is arranged in a single pass configuration and for generating the THz radiation having a THz frequency in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• the input radiation source device and the first conversion crystal device are configured such that a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device and the optical-to-THz-conversion process includes cascaded difference frequency generation of the optical input radiation using the multi-line frequency spectrum, wherein
• the input radiation source device comprises one of
• an ultrashort pulse laser oscillator having a pulse repetition rate at the THz frequency of the THz radiation to be generated,
• an ultrafast laser oscillator and a sequence of pulses is generated by a multi pulse generator splitting and stacking incoming optical pulses, and
• an optical pulse inter-leaver, or pulse shaper based on chirp and delaying an optical pulse.

A THz source apparatus, being configured for generating THz radiation, comprising

• an input radiation source device being arranged for generating optical input radiation, and
• a first conversion crystal device being arranged to be irradiated with the optical input radiation, wherein
• the first conversion crystal device is arranged in a single pass configuration and for generating the THz radiation having a THz frequency in response to the optical input radiation by an optical-to-THz-conversion process, wherein
• the input radiation source device and the first conversion crystal device are configured such that a multi-line frequency spectrum is provided by the optical input radiation in the first conversion crystal device and the optical-to-THz-conversion process includes cascaded difference frequency generation of the optical input radiation using the multi-line frequency spectrum further comprising
• at least one further conversion crystal device being arranged at an output side of the first conversion crystal device to be irradiated with at least one of the optical input radiation and the THz radiation, wherein
• the at least one further conversion crystal device is arranged for generating THz radiation in response to the optical input radiation by the optical-to-THz-conversion process.