A nonlinear crystal comprising a first curved face and an opposing second curved face is described. The first and second curved faces are arranged to provide the nonlinear crystal with rotational symmetry about at least one axis of the nonlinear crystal. The nonlinear crystal allows for frequency tuning of a generated optical field that is generated by propagating a fundamental optical field through the nonlinear crystal by rotation of the nonlinear crystal about an axis of rotation without any significant, or minimal, deviation being introduced to the generated optical field. These nonlinear crystals can therefore be incorporated into an external cavity frequency doubler or mixer without any need for the employment of optical compensation optics or servo control electronics to automatically realign the cavity mirrors.

The invention relates to a doubly resonant optical parametric oscillator (1) comprising a fan-out crystal (5, 55, 105) having an optical non-linearity of order 2 and placed in an optical cavity (6) able to reflect a pump (2), said crystal (5, 55, 105) comprising an entrance face (59) and an exit face (60), through which faces the optical axis passes, an upper face (57) and a lower face (58).

The main feature of an optical parametric oscillator (1) according to the invention is that said crystal (105) includes a grating of polarity-inverted lines (106) originating separately and in a narrowly spaced manner at a fictional upper line (61) that is parallel to the upper face (57) of the crystal (105), and ending separately and in a widely spaced manner either at a fictional lower line (63) that is parallel to the lower face (58) of the crystal (105), or at the entrance face (59) of the crystal, two successive lines (106) making between each other a constant angle, said grating starting with a first line (108) originating at the exit face (60) of the crystal (105) and extending towards the lower fictional straight line (63) while diverging from said exit face (60), all the other lines gradually and monotonically inclining from said first straight line (108) towards the entrance face (59) of the crystal (105).

A frequency conversion laser system is configured with a single mode (SM) laser source outputting a pulsed pump beam at a fundamental frequency and a nonlinear optical system operating to convert the fundamental frequency sequentially to a second harmonic (SH) and then third harmonic (TH). The nonlinear optical system includes an elongated SHG crystal traversed by the SM pulsed pump beam which generates the SH beam. The SHG crystal has an output surface inclined relative to a longitudinal axis of the SHG crystal at a first wedge angle different from a right angle. The nonlinear optical system further has an elongated THG crystal with an input surface which is impinged upon by a remainder of the pump and SHG beams which propagate through the THG crystal at a walk-off angle therebetween to generate a third harmonic (TH) beam, the input surface of the THG crystal being inclined to a longitudinal axis of the THG crystal at a second wedge angle. The output and input surfaces of respective SHG and THG crystals are inclined so as to minimize the walk-off angle between SH and IR pointing vectors in the THG crystal thereby improving the conversion efficiency and TH output beam's ellipticity.

A light emitting assembly, a backlight source and a display panel are provided. The light emitting assembly includes: a circuit board, at least one LED on the circuit board; the at least one LED has a main light emitting face substantially parallel to the circuit board and An oblique side light emitting face, the side light emitting face being located between the main light emitting face and the side light emitting face; a reflective film between the circuit board and the at least one LED; an acute angle is formed between the main light emitting face and the side light emitting face, and the side light emitting face is configured such that light emitted by the side light emitting face is directed away from the LED and is directed toward the circuit board, the reflective film being configured to reflect light emitted by the side light emitting face.

A wavelength conversion apparatus includes a multiplexer-demultiplexer configured to include a first port, a second port, and a third port, a looped non-linear optical medium including one end that is optically connected to the second port of the multiplexer-demultiplexer, another end that is optically connected to the third port of the multiplexer-demultiplexer, and a main axis that rotates by 90 degrees between the second port and the third port, a first filter configured to be inserted into the non-linear optical medium, and remove stimulated Brillouin backscattered light that is bidirectionally generated in the non-linear optical medium, and a second filter configured to take out, from output light that is multiplexed in the multiplexer-demultiplexer after propagating through the non-linear optical medium and is outputted from the first port, conversion light having a third frequency different from the frequencies of a signal light and an excitation light.

A light emitting assembly, a backlight source and a display panel are provided. The light emitting assembly includes: a circuit board, at least one LED on the circuit board; the at least one LED has a main light emitting face substantially parallel to the circuit board and An oblique side light emitting face, the side light emitting face being located between the main light emitting face and the side light emitting face; a reflective film between the circuit board and the at least one LED; an acute angle is formed between the main light emitting face and the side light emitting face, and the side light emitting face is configured such that light emitted by the side light emitting face is directed away from the LED and is directed toward the circuit board, the reflective film being configured to reflect light emitted by the side light emitting face.

According to some aspects, a transmissive and all-dielectric optical component/limiter with great cutoff efficiency using Vanadium Dioxide (VO.sub.2) as the active component is disclosed. In some embodiments, Vanadium dioxide is used for an optical limiter due to the large contrast in optical constants upon undergoing the semiconductor to metal phase transition. When triggered optically, this transition occurs within 60 fs, making the device suitable for an ultrafast laser environment. In addition, the phase transition threshold is tunable by applying stress or doping; therefore, the device cutoff intensity can be adjusted to fulfill specific requirements.

A nonlinear crystal comprising a first curved face and an opposing second curved face is described. The first and second curved faces are arranged to provide the nonlinear crystal with rotational symmetry about at least one axis of the nonlinear crystal. The nonlinear crystal allows for frequency tuning of a generated optical field that is generated by propagating a fundamental optical field through the nonlinear crystal by rotation of the nonlinear crystal about an axis of rotation without any significant, or minimal, deviation being introduced to the generated optical field. These nonlinear crystals can therefore be incorporated into an external cavity frequency doubler or mixer without any need for the employment of optical compensation optics or servo control electronics to automatically realign the cavity mirrors

An optical element according to an embodiment includes: a substrate having a first main surface and a second main surface on a side opposite to the first main surface and formed of single crystal, ceramic, or glass; and a heat sink bonded to the second main surface and having a refractive index lower than that of the first substrate, wherein a waveguide is formed in the substrate, wherein each of a pair of side surfaces of the waveguide in a direction intersecting with an extending direction of the waveguide and a thickness direction of the substrate is a modified surface obtained by modifying the substrate, and wherein the modified surface extends from the first main surface to the second main surface.

A wavelength conversion apparatus includes a multiplexer-demultiplexer configured to include a first port, a second port, and a third port, a looped non-linear optical medium including one end that is optically connected to the second port of the multiplexer-demultiplexer, another end that is optically connected to the third port of the multiplexer-demultiplexer, and a main axis that rotates by 90 degrees between the second port and the third port, a first filter configured to be inserted into the non-linear optical medium, and remove stimulated Brillouin backscattered light that is bidirectionally generated in the non-linear optical medium, and a second filter configured to take out, from output light that is multiplexed in the multiplexer-demultiplexer after propagating through the non-linear optical medium and is outputted from the first port, conversion light having a third frequency different from the frequencies of a signal light and an excitation light.