Q-switching device for waveguide CO2 lasers

Abstract

The application provides a Q-switching device for a waveguide CO2 laser, which can improve Q-switching output peak power, output stable and reliable high-quality light beams for a long time, and is beneficial to miniaturization of the laser. The application is suitable for the waveguide CO2 laser, the stroke of the piezoelectric ceramic can be changed between dozens of microns and dozens of millimeters, and the stroke distance is precisely controlled in a closed loop by a ceramic controller, so that the Q-switching is easily realized, the application has a simple structure, does not need to insert a complex Q-switching element in a resonant cavity, the coupling loss of a waveguide port is greatly reduced, and the Q-switching output peak power is improved. The piezoelectric ceramic has the characteristics of high precision, good stability and long service life, so that the stable and reliable high-quality light beams can be output for a long time, the piezoelectric ceramic has a small volume, the overall structure of the laser is more compact, and the miniaturization of the laser is beneficial.

Description

Technical Field

[0001] This invention relates to the field of laser Q-switching technology, and more specifically to a Q-switching device for waveguide CO2 lasers. Background Technology

[0002] Radio frequency (RF) waveguide CO2 lasers possess numerous advantages, including low excitation voltage, uniform discharge, long lifetime, compact structure, the ability for multiple waveguides to share an excitation source, and strong environmental adaptability, making them promising for applications in laser processing, laser detection, and communication radar. Among the various RF waveguide CO2 lasers, the RF slab waveguide CO2 laser has attracted significant attention due to its wide waveguide cavity electrodes, large discharge area, and ability to achieve high-power output.

[0003] To meet the high peak power requirements of practical applications, radio frequency waveguide CO2 lasers need to operate in pulsed mode. Currently, the main methods for achieving pulsed output in radio frequency waveguide CO2 lasers are electro-optic Q-switching, acousto-optic Q-switching, and mechanical Q-switching. Mechanical Q-switching is the earliest developed Q-switching technique, characterized by its simple structure, stability, reliability, and low cost. Traditional mechanical Q-switching achieves Q-switching by inserting a high-speed rotating chopper or mirror into the resonant cavity. For example... Figure 1 The diagram shows a schematic of a chopper-type mechanical Q-switching device. This device includes an output mirror, a waveguide cavity, a chopper, and a total reflection mirror. The output mirror and the total reflection mirror form the two ends of a resonant cavity. An optical chopper is inserted into the resonant cavity, and its high-speed rotation continuously cuts off the light beam within the cavity, achieving Q-switching. Rotating mirror Q-switching involves a high-speed motor driving the total reflection mirror to rotate. When the total reflection mirror is not perpendicular to the optical axis of the resonant cavity, the cavity loss is high, the Q value is low, and laser oscillation cannot be formed. However, when the total reflection mirror rotates to be perpendicular to the optical axis, the cavity loss is low, the Q value increases, and pulsed laser is output.

[0004] Unlike propagation in free space, when a beam propagates within a waveguide cavity, significant coupling loss occurs at the waveguide aperture. Furthermore, due to the large electrode width of RF slab waveguide CO2 lasers, they are much more sensitive to losses caused by inserted elements compared to RF narrow waveguide CO2 lasers. For traditional Q-switching, a certain distance must generally be left between the waveguide aperture and the total reflection mirror to accommodate the Q-switching element. This increased distance and the insertion of the Q-switching element significantly reduce the waveguide aperture coupling efficiency, resulting in a substantial decrease in laser output power, or even complete failure to output laser light. For chopper-type mechanical Q-switching, the chopper inserted into the resonant cavity not only reduces the waveguide aperture coupling efficiency, leading to a decrease in output power, but also increases the laser's size, hindering miniaturization. For rotating mirror Q-switching, to achieve free rotation of the mirror, the distance between the total reflection mirror and the waveguide aperture must also be appropriately increased, which also causes significant coupling loss. Moreover, the rotation of the mirror causes a fluctuation in the output beam axis relative to the resonant cavity axis, resulting in lower output accuracy. Additionally, due to motor limitations, rotating mirror Q-switching has a low repetition frequency, short bearing life, and high noise. Summary of the Invention

[0005] In view of this, the present invention proposes a Q-switching device for waveguide CO2 lasers, which can improve the peak power of Q-switched output, output a stable and reliable high-quality beam for a long time, and is also conducive to the miniaturization of lasers.

[0006] To achieve the above objectives, this invention provides a Q-switching device for a waveguide CO2 laser, comprising an output mirror, a waveguide plate, a waveguide, a total reflection mirror, a piezoelectric ceramic, and a piezoelectric ceramic controller. One side of the waveguide is a total reflection mirror, and the other side is an output mirror. The total reflection mirror, output mirror, and waveguide constitute a resonant cavity for photon oscillation within the cavity, ultimately outputting laser light from the output mirror. One end of the piezoelectric ceramic is fixed to the back of the total reflection mirror as a movable end, while the other side remains stationary. The piezoelectric effect changes the extension / retraction of the movable end, thereby altering the distance between the total reflection mirror and the waveguide opening. The piezoelectric ceramic and the piezoelectric ceramic controller are connected by a cable, and the controller eliminates travel errors through closed-loop control. By controlling the extension / retraction of the piezoelectric ceramic, the total reflection mirror reciprocates along the optical axis, changing the distance between the total reflection mirror and the waveguide opening, thus achieving Q-switching. The central axes of the output mirror, total reflection mirror, waveguide, and piezoelectric ceramic should be located on the optical axis, and the reflective surfaces of the output mirror and total reflection mirror are placed perpendicular to the optical axis.

[0007] The waveguide is a radio frequency slab waveguide.

[0008] Among them, the natural frequency of piezoelectric ceramics reaches above kHz.

[0009] The piezoelectric ceramic is mainly composed of lead zirconate titanate.

[0010] In this embodiment, the piezoelectric ceramic is replaced by a piezoelectric ceramic actuator.

[0011] The slab waveguide includes two parallel flat metal electrodes, with parallel non-metallic materials sandwiched between them. The metal material is aluminum, and the non-metallic material is alumina ceramic.

[0012] Beneficial effects:

[0013] 1. This invention is applicable to waveguide CO2 lasers. The stroke of the piezoelectric ceramic can vary from tens of micrometers to tens of millimeters, and the stroke distance is precisely controlled by a closed-loop ceramic controller, facilitating Q-switching. Furthermore, the invention has a simple structure, eliminating the need for complex Q-switching elements in the resonant cavity, significantly reducing coupling loss at the waveguide port and improving the peak power of the Q-switched output. Piezoelectric ceramics are characterized by high precision, good stability, and long lifespan, thus enabling the output of a stable and reliable high-quality beam for extended periods. Moreover, the small size of the piezoelectric ceramic makes the overall structure of the laser more compact, contributing to laser miniaturization.

[0014] 2. This invention is particularly applicable to radio frequency slab waveguide CO2 lasers. The slab waveguide cavity is very sensitive to coupling loss, so changes in the resonant cavity distance will cause drastic changes in the waveguide port coupling loss.

[0015] 3. The piezoelectric ceramic of the present invention has a selectable natural frequency range from hundreds of Hz to hundreds of kHz, which can obtain a high repetition frequency and is beneficial for outputting beams with narrow pulse width and high peak power. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the principle of a chopper-type mechanical Q-switching device in the prior art.

[0017] Figure 2 This is a schematic diagram of the principle of the device of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] This invention achieves mechanical Q-switching of a waveguide CO2 laser by altering the distance from the total reflection mirror to the waveguide aperture using piezoelectric ceramics. The main structure of a slab waveguide typically consists of two parallel flat metal electrodes placed one above the other, sandwiched between parallel non-metallic materials. Aluminum is preferred as the metallic material, and alumina ceramic is preferred as the non-metallic material. The wide aperture of the slab waveguide electrode allows for large-area discharge and high-power laser output. This invention is particularly suitable for radio frequency slab waveguide CO2 lasers. The slab waveguide cavity is highly sensitive to coupling loss; therefore, changes in the resonant cavity distance cause drastic changes in the waveguide aperture coupling loss.

[0020] The present invention uses a radio frequency slab waveguide CO2 laser as an example to illustrate the device. A schematic diagram of the device structure is shown below. Figure 2 As shown, it includes an output mirror, a waveguide sheet, a slab waveguide, a total reflection mirror, a piezoelectric ceramic, and a piezoelectric ceramic controller.

[0021] The slab waveguide consists of a total reflection mirror on one side and an output mirror on the other. The total reflection mirror, output mirror, and slab waveguide together form a resonant cavity, enabling photon oscillation within the cavity and ultimately outputting laser light from the output mirror. A piezoelectric ceramic is fixed at one end to the back of the total reflection mirror as a movable end, while the other end remains stationary. The piezoelectric effect alters the extension and retraction of the movable end, thus changing the distance between the total reflection mirror and the waveguide opening. The piezoelectric ceramic is connected to a piezoelectric ceramic controller via a cable. The controller, through closed-loop control, eliminates travel errors caused by hysteresis and creep effects of the piezoelectric ceramic, precisely controlling the distance. The controller controls the extension and retraction of the piezoelectric ceramic, causing the total reflection mirror to reciprocate rapidly along the optical axis. As the distance *d* between the total reflection mirror and the waveguide opening increases, the coupling efficiency at the waveguide opening decreases sharply. Low coupling efficiency results in high cavity loss, low Q-value, and energy accumulation within the cavity without laser output. Conversely, when the distance *d* is small, the waveguide opening coupling efficiency is high, the cavity loss is low, the Q-value is high, and laser light can be output. Therefore, by controlling the expansion and contraction of the piezoelectric ceramic, the distance from the total reflection mirror to the waveguide port can be changed, thereby adjusting the cavity loss and achieving the purpose of Q-switching. The central axes of the output mirror, total reflection mirror, slab waveguide, and piezoelectric ceramic should be located on the optical axis, and the reflective surfaces of the output mirror and total reflection mirror should be placed as perpendicular to the optical axis as possible.

[0022] Piezoelectric ceramics are preferably made primarily of lead zirconate titanate (PZT). The natural frequency of piezoelectric ceramics can reach above kHz, thus fully meeting the requirements for rapid switching of Q-switching.

[0023] Furthermore, the piezoelectric ceramic can also be selected from piezoelectric ceramic actuators or other suitable devices that enable the total reflection mirror to reciprocate; the non-metallic materials sandwiched in the upper and lower metal electrodes of the waveguide cavity can also be suitable metallic materials.

[0024] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Q-switching device for a waveguide CO2 laser, characterized in that, The system includes an output mirror, a waveguide plate, a waveguide, a total reflection mirror, piezoelectric ceramics, and a piezoelectric ceramic controller. One side of the waveguide is the total reflection mirror, and the other side is the output mirror. The total reflection mirror, output mirror, and waveguide form a resonant cavity to achieve photon oscillation within the cavity, ultimately outputting laser light from the output mirror. One end of the piezoelectric ceramic is fixed to the back of the total reflection mirror as a movable end, while the other side remains stationary. The piezoelectric effect changes the extension or retraction of the movable end, thereby altering the distance between the total reflection mirror and the waveguide opening. Communication between the piezoelectric ceramic and the piezoelectric ceramic controller is... The piezoelectric ceramic controller, connected via cable, eliminates travel errors caused by the hysteresis and creep effects of the piezoelectric ceramic through closed-loop control. By controlling the expansion and contraction of the piezoelectric ceramic, the total reflection mirror is driven to reciprocate along the optical axis. By periodically changing the distance between the total reflection mirror and the waveguide port, the coupling loss of the waveguide port and the Q value of the resonant cavity are changed, thereby achieving periodic modulation of laser output and generating high peak power pulsed laser. The central axes of the output mirror, total reflection mirror, waveguide, and piezoelectric ceramic should be located on the optical axis, and the reflective surfaces of the output mirror and total reflection mirror should be placed perpendicular to the optical axis. The waveguide is a radio frequency slab waveguide; the slab waveguide includes two parallel flat metal electrodes, with parallel non-metallic materials sandwiched between the electrodes, wherein the metal material is aluminum and the non-metallic material is alumina ceramic.

2. The apparatus as claimed in claim 1, characterized in that, The natural frequency of piezoelectric ceramics can reach over kHz.

3. The apparatus as described in claim 1, characterized in that, The piezoelectric ceramic is mainly composed of lead zirconate titanate.

4. The apparatus as claimed in claim 1, characterized in that, The piezoelectric ceramic is replaced with a piezoelectric ceramic actuator.

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