A method of making a quasi-phase-matching (QPM) structure comprising the steps of: applying a pattern to a substrate to define a plurality of growth regions and a plurality of voids; growing in a growth chamber a crystalline inorganic material on only the growth regions in the pattern, the crystalline inorganic material having a first polarity; applying an electric field within the growth chamber containing the patterned substrate with the crystalline inorganic material, wherein the electric field reaches throughout the growth chamber; and growing a crystalline organic material having a second polarity in the voids formed in the inorganic material under the influence of the electric field to influence the magnitude and the direction of the second polarity of the crystalline organic material, wherein the second polarity of the crystalline organic material is influenced to be different from the first polarity of the crystalline inorganic material in magnitude and/or direction.

Systems and methods are provided for optimizing the energy output of a laser system, such as a Light Detection and Ranging (LIDAR) system, by allowing the laser system to be tuned while the laser is in operation. For example, in an embodiment, a sensor, such as a photoresistor, is used to perform a scan to determine whether turning the crystal will result in increased energy. Crystal turners, such as servo motors, can be used to turn the crystal until the energy stops increasing.

A collinear T-cavity VECSEL system generating intracavity Hermite-Gaussian modes at multiple wavelengths, configured to vary each of these wavelengths individually and independently. A mode converter element and/or an astigmatic mode converter is/are aligned intracavity to reversibly convert the Gaussian modes to HG modes to Laguerre-Gaussian modes, the latter forming the system output having any of the wavelengths provided by the spectrum resulting from nonlinear frequency-mixing intracavity (including generation of UV, visible, mid-IR light). The laser system delivers Watt-level output power in tunable high-order transverse mode distribution.

A surface-emitting quantum cascade laser of an embodiment comprises a substrate, an active layer, and a photonic crystal layer. The active layer has optical nonlinearity, and is capable of emitting a first and a second infrared laser light. The photonic crystal layer includes a first and a second region. The rectangular grating of the first region is orthogonal to the rectangular grating of the second region. The first infrared laser light has a wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating. The second infrared laser light has a wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating.

A collinear T-cavity VECSEL system generating intracavity Hermite-Gaussian modes at multiple wavelengths, configured to vary each of these wavelengths individually and independently. A mode converter element and/or an astigmatic mode converter is/are aligned intracavity to reversibly convert the Gaussian modes to HG modes to Laguerre-Gaussian modes, the latter forming the system output having any of the wavelengths provided by the spectrum resulting from nonlinear frequency-mixing intracavity (including generation of UV, visible, mid-IR light). The laser system delivers Watt-level output power in tunable high-order transverse mode distribution.

A method of manufacturing a quantum cascade laser beam source (1) includes: preparing a semiconductor stacked body (20); forming a pair of first excavated portions (41 and 42) and a ridge portion which is interposed between the pair of first excavated portions (41 and 42); forming channel structures (51 and 52) and circumferential edge portions (61 and 62) which are formed to interpose the channel structures (51 and 52) between the ridge portion (30) and the circumferential edge portion; forming an electrode pattern (81) in contact with a first area (29a) and forming an electrode pattern (82) in contact with a second area (22a); fixing a crystal growth surface side to a support substrate (91); removing an Fe-doped (semi-insulating) InP single-crystal substrate (21); fixing a Si substrate (93); and peeling the support substrate (91).

An artificial saturable absorber uses additive pulse mode-locking to enable pulse operation of an on-chip laser operation. Four different artificial saturable absorbers are disclosed. The first includes an integrated coupler, two arms each containing some implementation of the end-reflector, and a phase bias element in one arm. The second includes an integrated directional coupler, two integrated waveguide arms, and another integrated coupler as an output. The third includes an integrated birefringent element, integrated birefringent-free waveguide, and integrated polarizer. And the fourth includes a multimode waveguide that allows for different modes to propagate in such a way that the difference in the spatial distribution of intensity causes a nonlinear phase difference between the modes. These are just some examples of an on-chip fully integrated artificial saturable absorber with instantaneous recovery time that allow for generation of sub-femtosecond optical pulses at high repetition rates using passive mode-locking.

A surface-emitting quantum cascade laser of an embodiment comprises a substrate, an active layer, and a photonic crystal layer. The active layer has optical nonlinearity, and is capable of emitting a first and a second infrared laser light. The photonic crystal layer includes a first and a second region. The rectangular grating of the first region is orthogonal to the rectangular grating of the second region. The first infrared laser light has a wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating. The second infrared laser light has a wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating.

A terahertz quantum cascade laser device includes a substrate, q semiconductor stacked body and a first electrode. The semiconductor stacked body includes an active layer and a first clad layer. The active layer is provided on the substrate and is configured to emit infrared laser light by an intersubband optical transition. The first clad layer is provided on the active layer. A ridge waveguide is provided in the semiconductor stacked body. A first distributed feedback region and a second distributed feedback region are provided at an upper surface of the first clad layer to be separated from each other along an extension direction of the ridge waveguide. The first electrode is provided at the upper surface of the first clad layer. A planar size of the first distributed feedback region is smaller than a planar size of the second distributed feedback region.

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 ?m 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.