Jinglun Liu

Axisymmetric-fold combination laser resonator

We present an axisymmetric-fold combination laser resonator. For a laser with the resonator, it can give a strong output, a good light beam, and a small device volume. The energy flux of the beam is high and the diameter is small in the near field; it diverges with a small angle, but transforming the beam from a divergent beam into a parallel or convergent beam is convenient. The resonator is suitable for various kinds of lasers.

Research on near-field distributions of axisymmetric folded-combined CO2 laser

The near-field-intensity distributions of diffusion-cooled axisymmetric folded-combined CO 2 lasers are investigated. Formulas representing the near-field distributions for some typical kinds of folded-combined CO 2 lasers are suggested, and the near-field-intensity profiles are calculated numerically and simulated. For several centimeters from the output mirror along the direction of the symmetric axis, the intensity in the output beam is very high and its radius (or width) is very small (approximately double waist radius). The frequency differences between different cavities would induce fluctuations of the intensity distribution, but the fluctuations are not distinctive. The near-field beam can be used directly in some industrial material processing.

Study of performance of a He-Ne laser having an annular gain zone

A He-Ne laser with an annular gain zone is studied theoretically. It is demonstrated that the He-Ne medium in the annular discharge zone possesses enough gain to maintain laser oscillation. A multipass ring resonator, which is composed of two annular spherical mirrors, is described, and it is shown that the resonator is suitable for extracting optical energy from the He-Ne medium in the annular gain zone. Considering the availability of population inversion in the traveling-wave cavity and the influence of the crossover of the folded light beam in the resonator on the output power, a calculation formula for the output power of the laser with the multipass ring resonator is given. Calculating results prove that a 1 W output of the He-Ne laser can be obtained by a 1 m length annular discharge zone.

Proposal to obtain a hollow laser beam from a hollow cone-shaped resonator

A CO2 laser with a hollow cone-shaped resonator (HCR) for producing a hollow laser beam (HLB) is proposed. The HCR consists of a totally reflective mirror and a partially reflective mirror at the two ends of a hollow cone-shaped discharge tube. In a longitudinal section of the HCR along its axis of symmetry it can be regarded as a folded cavity. Employing an standard optical system, the HLBs can be focused to meet the requirements of various applications. Analysis shows that not only can an HLB be obtained, but also the radius of the dark region of the focused HLB is easy to adjust. The hollow cone-shaped CO2 laser may be used as a new type of optical tweezers.

Hollow circular-truncated cone resonator and its hollow variable biconical laser beam

Abstract. To obtain a hollow variable biconical laser beam (HVBLB), a CO2 laser having a hollow circular-truncated cone resonator (HCTCR) is presented. This HCTCR comprises a rotationally symmetric total-reflecting concave mirror at the bottom, a rotationally symmetric part-reflecting convex mirror at the top, and a hollow circular-truncated cone discharge tube at the middle. The cross section of this generated biconical laser beam changes from annulus to circular to annulus and the size of this cross section from big to small to large as the propagation distance increases. So, a kind of laser beam with variable center intensity from zero to peak value to zero is obtained and is known as HVBLB. Due to the inclusion of part of the hollow laser beam (HLB) and solid laser beam, this HVBLB requires no additional beam-shaping element and has broad applications such as optical trapping and commercial manufacturing.