The invention relates to a method for modulating the resonant frequency of an optical resonator (1) in accordance with a periodic, not necessarily harmonic, modulation signal (U.sub.mod(t)). Fast modulation of an optical resonator is intended to be made possible in which the current resonant frequency follows the modulation signal (U.sub.mod(t)) as precisely as possible, and specifically at a fundamental frequency of the modulation signal in the kHz range. To do this, the invention proposes the following method steps: deriving an error signal (E(t)) from a light field circulating in the resonator (1), wherein the error signal (E(t)) indicates the deviation of the optical frequency of the light field from a target value, deriving a first actuating signal (S.sub.1(t)) from the error signal (E(t)) by means of a controller (6), generating a second actuating signal (S.sub.2(t)), which has actuating-signal components at one or more harmonics (f.sub.mod, 2f.sub.mod, . . . ) of the fundamental frequency (f.sub.mod) of the modulation signal (U.sub.mod(t)), and applying a superposition signal made up of the first and the second actuating signal (S.sub.1(t), S.sub.2(t)) to an actuator (3) that changes the optical path length of the resonator (1). In other words, the invention makes use of a combination of control and narrow-band feed-forward control tuned to the spectrum of the modulation signal (U.sub.mod(t)) and of the error signal (E(t)) to modulate the resonant frequency. Preferably, the feed-forward control used for generating the second actuating signal (S.sub.2(t)) is automatically adapted in accordance with the error signal (E(t)). In addition, the invention relates to an accordingly configured optical system.

A fractional handpiece and systems thereof for skin treatment include a passively Q-switched laser assembly operatively connected to a pump laser source to receive a pump laser beam having a first wavelength and a beam splitting assembly operable to split a solid beam emitted by the passively Q-switched laser assembly and form an array of micro-beams across a segment of skin. The passively Q-switched laser assembly generates a high power sub-nanosecond pulsed laser beam having a second wavelength.

A hybrid laser printing (HLP) technology that utilizes ultrafast laser in sequential additive-subtractive modes to create 3D hydrogel constructs. The approach involves the synergistic use of additive crosslinking and subtractive ablation processes that are conventionally mutually exclusive. HLP can be operated at virtually any penetration depth and allow fabrication of multi-layer hydrogel constructs at micrometer resolution. HLP was used to print ready-to-use functional chips using commonly used hydrogels for potential cellular communication and migration applications. HLP was also found to be compatible with in situ printing of cell-laden hydrogel constructs. HLP makes shaping of soft hydrogels into 3D multiscale functional devices possible.

A hybrid laser printing (HLP) technology that utilizes ultrafast laser in sequential additive-subtractive modes to create 3D hydrogel constructs. The approach involves the synergistic use of additive crosslinking and subtractive ablation processes that are conventionally mutually exclusive. HLP can be operated at virtually any penetration depth and allow fabrication of multi-layer hydrogel constructs at micrometer resolution. HLP was used to print ready-to-use functional chips using commonly used hydrogels for potential cellular communication and migration applications. HLP was also found to be compatible with in situ printing of cell-laden hydrogel constructs. HLP makes shaping of soft hydrogels into 3D multiscale functional devices possible.

A nonlinear crystal comprising a first end face and an opposing second end face is described. The first and second end faces are separated along an optical axis of the nonlinear crystal by a length in the range of 0.25 mm and 2 mm. Although the length of the nonlinear crystal results in a reduction in the nonlinear effects induced on an optical field propagating through the crystal it also provides for reduced deviation experienced by the generated optical field when the nonlinear crystal is rotated. Therefore, when the nonlinear crystals are incorporated within an enhancement cavity their reduced length allows for the deviation of the output field to be minimised by servo control electronics arranged to adjust a single cavity mirror. This significantly reduces the complexity, and thus expensive of the servo control electronics when compared to those employed with the prior art enhancement cavities.

Disclosed is a device for interaction between a laser beam and a hyperfine energy transition of a chemical species. The device further includes an electro-optic modulator with a single sideband with an input optical waveguide suitable for receiving a source laser beam and an output optical waveguide suitable for generating an output laser beam and an electronic system suitable for generating and applying, simultaneously, a first modulated electrical signal, sin(Ω.sub.1t)) to a first hyperfrequency pulse on a first high-frequency electrode of the electro-optic modulator and, respectively, another modulated electrical signal, cos(Ω.sub.1t)) to the first pulse on another high-frequency electrode of the electro-optic modulator, in such a way as to frequency-switch the output laser beam to a first optical frequency offset from the first pulse with respect to the initial optical frequency.

Disclosed is a device for interaction between a laser beam and a hyperfine energy transition of a chemical species. The device further includes an electro-optic modulator with a single sideband with an input optical waveguide suitable for receiving a source laser beam and an output optical waveguide suitable for generating an output laser beam and an electronic system suitable for generating and applying, simultaneously, a first modulated electrical signal, sin(Ω.sub.1t)) to a first hyperfrequency pulse on a first high-frequency electrode of the electro-optic modulator and, respectively, another modulated electrical signal, cos(Ω.sub.1t)) to the first pulse on another high-frequency electrode of the electro-optic modulator, in such a way as to frequency-switch the output laser beam to a first optical frequency offset from the first pulse with respect to the initial optical frequency.

A wavelength conversion system according to an aspect of the present disclosure includes a first crystal holder holding a first non-linear crystal, a second crystal holder holding a second non-linear crystal, a third crystal holder holding a third non-linear crystal, and a container housing the holders. The container has an entrance window and an emission window. The first non-linear crystal, the second non-linear crystal, and the third non-linear crystal are disposed in this order on an optical path of a laser beam traveling from the entrance window to the emission window. The crystal holders are rotatable. A first rotational axis that is a rotational axis of the first crystal holder is orthogonal to a second rotational axis that is a rotational axis of the second crystal holder, and the first rotational axis is parallel to a third rotational axis that is a rotational axis of the third crystal holder.

A wavelength conversion apparatus according to an aspect of the present disclosure is a wavelength conversion apparatus that performs wavelength conversion of light through a non-linear crystal and including a first non-linear crystal, a container in which the first non-linear crystal is housed, a crystal holding member provided inside the container for fixing the first non-linear crystal, a first window provided to the container for guiding light to the first non-linear crystal from outside of the container, a second window provided to the container for guiding light output from the first non-linear crystal to outside of the container, a first heater provided inside the container for heating the first non-linear crystal, a battery that supplies electric power to the first heater, and a first controller that controls electric power supply to the first heater.

A wavelength conversion apparatus according to an aspect of the present disclosure is a wavelength conversion apparatus that performs wavelength conversion of light through a non-linear crystal and including a first non-linear crystal, a container in which the first non-linear crystal is housed, a crystal holding member provided inside the container for fixing the first non-linear crystal, a first window provided to the container for guiding light to the first non-linear crystal from outside of the container, a second window provided to the container for guiding light output from the first non-linear crystal to outside of the container, a first heater provided inside the container for heating the first non-linear crystal, a battery that supplies electric power to the first heater, and a first controller that controls electric power supply to the first heater.