In a terahertz wave generation apparatus including a first non-linear optical crystal 3 on which first laser L1 and second laser L2 from laser generation means 2 are incident to generate terahertz wave TH1, the laser generation means includes a second non-linear optical crystal 7 on which laser having the same wavelength as that of the second laser is incident to generate idler light L1 including a plurality of wavelengths, and makes the idler light L1 generated from the second non-linear optical crystal incident on the first non-linear optical crystal as the first laser L1, to generate terahertz wave including a plurality of wavelengths from the first non-linear optical crystal 3, and wavelength selection means including a transmission section which transmits an idler light having the specific wavelength in the idler light including the plurality of wavelengths can be provided, as needed. Thus, terahertz wave having a high output power and including a plurality of wavelengths can be obtained, and the wavelength selection means easily obtains a required terahertz wave having the specific wavelength.

A method and system for delivering laser pulses achieves the delivery of high quality laser pulses at the location of an application. The method includes the steps of: generating laser pulses, amplifying the laser pulses, temporally stretching the amplified laser pulses, and propagating the amplified laser pulses through an optical delivery fiber of desired length, wherein the laser pulses are temporally compressed in the optical delivery fiber and wherein the laser pulses undergo nonlinear spectral broadening in the optical delivery fiber.

According to various embodiments, there is provided a layer arrangement including a graphene layer; a gating electrode layer configured to provide a tuning voltage to the graphene layer; a laser layer configured to provide an electromagnetic wave; and a concentric-circular grating layer configured to couple the electromagnetic wave to the graphene layer.

A laser device for generating an optical wave including at least two frequencies, such laser device including: a first element including a gain region, a second mirror, distinct from the first element, and arranged so as to form with a first mirror an optical cavity including the gain region; means for pumping the gain region so as to generate the optical wave; means for shaping the light intensity of the optical wave arranged for selecting at least two transverse modes of the optical wave; and means for shaping the longitudinal and/or transversal phase profile of the optical wave and arranged for adjusting at least two transverse modes of the optical wave.

A wireless communication device includes a quantum cascade laser (QCL) configured to generate a terahertz (THz) or microwave carrier signal. The QCL includes a laser waveguide, a laser optical gain medium incorporated in the laser waveguide, and at least one electrode. An antenna may be integrated with the electrode. The device may be a transmitter, the electrode configured to receive an input baseband signal, the QCL configured to couple the THz or microwave carrier signal and the input baseband signal into a THz or microwave communication signal, and the antenna configured to transmit the THz or microwave communication signal. The device may be a receiver, the antenna configured to receive a THz or microwave communication signal, and the QCL configured to de-couple the THz or microwave communication signal from the THz or microwave carrier signal into an output baseband signal.

A terahertz radiator is based on coherent Smith-Purcell radiation amplified by stimulation. The terahertz radiator includes an electron emission source configured to emit electron beams and a pumping source configured to emit pumping signals. The pumping signal interacts with a primary grating structure to obtain preliminarily bunched electrons. The preliminarily bunched electrons interact with the primary grating structure to generate coherent Smith-Purcell radiation. The coherent Smith-Purcell radiation and the pumping signals vertically resonate in a primary resonant cavity structure, so that the electron bunching density is increased, and in turn, the coherent Smith-Purcell radiation is enhanced. A positive feedback process is formed by free electrons and the coherent Smith-Purcell radiation, and the coherent Smith-Purcell radiation amplified by stimulation and periodic bunched electron bunches are obtained. The terahertz radiator can be used to realize a stimulated amplification phenomenon under the conditions of small current and large beam spots.

A laser module including a quantum cascade laser that includes a substrate having a main surface, a first clad layer provided on the main surface, an active layer provided on the first clad layer, and a second clad layer provided on the active layer, and a lens that has a lens plane disposed at a position facing the end surface of the active layer. An end surface of the active layer constitutes a resonator that causes light of a first frequency and light of a second frequency to oscillate, and the active layer is configured to generate a terahertz wave of a differential frequency between the first frequency and the second frequency. The substrate is in direct contact or indirect contact with the lens plane, and the end surface of the active layer is inclined with respect to a portion facing the end surface in the lens plane.

The laser module includes a QCL element, a diffraction grating unit including a movable diffraction grating, a first lens that transmits light emitted from an end surface of the QCL element and light returning from the movable diffraction grating to the QCL element, a second lens that transmits terahertz waves emitted from the QCL element, a first holder, and a package. The first holder has a support surface on which the QCL element is mounted and a side surface connected to the support surface and facing the first lens in a resonance direction. A distance from an intersection point between the side surface and the support surface to the end surface along the resonance direction is smaller than a distance between the intersection point and the first lens along the resonance direction.

A light source for high power coherent light can include multiparticle relativistic bunches of electrons generating high intensity propagating fields. Coherent emission between electrons may also be utilized. The source may be independent of any medium or media to remove all constraints on the wavelength of the light emitted. And at least a portion of a single alternating magnetic field for accelerating the electron bunches can be included. The color or wavelength of the produced light can be determined solely by the parameters of the electron bunches and the alternating field. The source can be used for imaging, such as medical imaging or for security, including concealed weapons, and for quality control.

A quantum cascade laser device includes a semiconductor substrate, an active layer provided on the semiconductor substrate, and an upper clad layer provided on a side of the active layer opposite to the semiconductor substrate side and having a doping concentration of impurities of less than 1×10.sup.17 cm.sup.−3. Unit laminates included in the active layer each include a first emission upper level, a second emission upper level, and at least one emission lower level in their subband level structure. The active layer is configured to generate light having a center wavelength of 10 μm or more due to electron transition between at least two levels of the first emission upper level, the second emission upper level, and the at least one emission lower level in the light emission layer in each of the unit laminates.