• Korean Journal of Optics and Photonics
• /
• v.5 no.1
• /
• pp.60-66
• /
• 1994

First, the beam waist size of TE$M_{00}$ Nd:YAG laser mode with Positive Branch Unstable Resonator was calculated. and then, the output power, fundamental mode and multimode beam quality factor of PBUR were measured and compared with thouse of reference resonator with plane pallalel mirrors. In characterizing the beam quality, the $M^2$ concept was used. The focusability of laser beam in unstable resonators was discussed with this $M^2$.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.447-454
• /
• 2006

We obtained analytic solutions of boundary conditions to the stable region of Z-fold $Cr^{4+}$ : YAG laser cavity when the conditions are with and without thermal tensing effect. Also we investigated the influence of the thermal tensing effect on the stability of cavity, beam waist, and astigmatic compensation using aberration transformation matrices. The thermal tensing effect almost has no influence on the stable region of the cavity when the crystal is located in the middle of two concave mirrors and when the distances from the concave mirror to the reflecting mirror and the output coupler are the same. The beam waist, however, is affected more in a tangential plane than in a sagittal plane, and so it is difficult to have astigmatic compensation when the thermal tensing effect exists. This result means that the thermal tensing effect should be considered even for the Kerr-lens mode-locking.

• Korean Journal of Optics and Photonics
• /
• v.3 no.4
• /
• pp.222-226
• /
• 1992

The lasing characteristics of a Nd:phosphate glass laser pumped by 514 nm of an $Ar^{+}$ laser has been investigated. The oscillator consists of a Nd:glass gain medium set at Brewster angle, and two concave mirrors, and a flat mirror with a reflectance of 98%. The $Ar^{+}$ laser pumping beam is focused longitudinally at the beam waist of laser mode for efficient pumping. The pumping beam is chopped at 100 Hz to reduce the heat loading to prevent the thermal damage of the gain medium by the latent heat from the absorbed pumping beam. The maximum laser output power of 70 mW at 1.5 W pumping and the threshold input power of 520 mW have been obtained.

• International Journal of Precision Engineering and Manufacturing
• /
• v.8 no.2
• /
• pp.54-58
• /
• 2007

This paper describes an atomic force microscope (AFM)-based instrument for measuring the nanoscale cutting edge profiles of diamond cutting tools. The instrument consists of a combined AFM unit and an optical sensor to align the AFM tip with the top of the diamond cutting tool edge over a submicron range. In the optical sensor, a aser beam is emitted from a laser diode along the Y-axis and focused to a small beam spot with a diameter of approximately $10{\mu}m$ at the beam waist, which is then received by a photodiode. The top of the tool edge is first brought into the center of the beam waist by adjusting it in the X-Z-plane while monitoring the variation in the photodiode output. The cutting tool is then withdrawn and its top edge position at the beam center is recorded. The AFM tip can also be positioned at the beam center in a similar manner to align it with the top of the cutting edge. To reduce electronic noise interference on the photodiode output and thereby enhance the alignment accuracy, a technique is applied that can modulate the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements of a diamond cutting tool were carried out to verify the performance of the proposed system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.11
• /
• pp.1324-1333
• /
• 2010

In this paper, three kinds of beam coupling losses which occur in a quasi-optics circuit for millimeter wave receiver system have been intensively investigated. First, the beam coupling losses which are caused by mismatch of beam waists radii and their positions between those of one and the other have been evaluated. It shows that beam coupling losses due to mismatch of beam waists radii and their positions between two quasi-optics circuits can be minimized if beam waist radius is chosen as larger than 3 times the operation wavelength. Second, the beam coupling losses have been studied when the axis of propagation of one beam is tilted with respect to that of the other beam. It is noted that smaller beam waist radius results in greater tolerance to tilts and angular misalignments. Third, the beam coupling cases in which two beams are offset if their axes of propagation are parallel but one is displaced relative to the other have been investigated. It is confirmed that beam waists radii with larger than 3 times operation wavelength are less sensitive to lateral offsets.

• Proceedings of the KIEE Conference
• /
• 1993.11a
• /
• pp.356-358
• /
• 1993

With a focused laser beam, we make a microscopic change on a thin film, and organize the overall system that can observe the change with a microscope. This system utilizes the energy of a laser beam which is focused by a simple lense system. That is a laser beam which has its waist at working distance of a lense. The microscopic change induced by the energy of laser beam focused through a lense can be observed in real time. The experiment with this system shows that the 10mW He-Ne 632.8nm laser can change the black vinyl instantaneously.

• Proceedings of the KIEE Conference
• /
• 2000.11c
• /
• pp.594-596
• /
• 2000

The best simulation condition for the fiber collimator that uses ball lenses was investigated. This kind of fiber collimator can be used in a Micro-Optical-Cross-Connects(MOXC). MOXC is composed of collimating ball lenses, micro mirrors and single-mode fibers. In order to design a MOXC, it is very important to calculate beam path, beam radius, divergence angle that determines the insertion loss of the MOXC. Since the beam profile from the fiber facet is not exact Gaussian profile, it was found that the simulation condition in which beam waist exists on the fiber facet, ignoring Numerical Aperture(NA), gives best agreement with the experimental results. Beam radii were measured with conventional knife edge method.

• Korean Journal of Optics and Photonics
• /
• v.16 no.5
• /
• pp.456-461
• /
• 2005

We numerically investigate the characteristic of single Nd:YAG rod laser with the convex-plane resonator configuration in order to get the best condition for high efficient intra-cavity second harmonic generation(SHG). The beam quality is analyzed with ABCD matrixes including the thermal lensing characteristic of Nd:YAG rod. The analysis is focused on stability, M2, beam waist and mode-volume of laser beam inside the resonator. The best conditions for SHG is obtained when a laser rod is set near the curved laser mirror.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.130-131
• /
• 2000

One of the more promising proposals for guiding and focusing neutral atoms involves dark hollow laser beams. When the frequency of the laser is detuned to the blue of resonance, the dipole force the atoms feel in the light confines them to the dark core where the atoms can be transported with minimal interaction with the light. The ability of the all-light atom guides to transport large number of ultracold atoms for long distances without physical walls leads to the possibility of a versatile tool for atom lithography, atom interferometry, atomic spectroscopy as well as for transporting and manipulating Bose-Einstein condensates. Furthermore since the atoms transported in all-light atom guides do not come into contact with matter, they can in principle be used to transport antimatter as well. The ability to vary the core size of the hollow beam makes the all-light atom guide potentially useful for focusing neutral atoms. The atoms could be focused as tight as the core size of the hollow beam at its waist. This new focusing scheme, called the atom funnel, would not show spherical and chromatic aberrations that conventional harmonic focusing suffers from. (omitted)

• Journal of the Optical Society of Korea
• /
• v.16 no.3
• /
• pp.305-312
• /
• 2012

We numerically demonstrate the performance of a plasmonic lens composed of an array of nanoslits perforated on thin metallic film with slanted cuts on the output surface. Embedding Kerr nonlinear material in nanoslits is employed to modulate the output beam. A two dimensional nonlinear-dispersive finite-difference time-domain (2D N-D-FDTD) method is utilized. The performance parameters of the proposed lens such as focal length, full-width half-maximum, depth of focus and the efficiency of focusing are investigated. The structure is illuminated by a TM-polarized plane wave and a Gaussian beam. The effect of the beam waist of the Gaussian beam and the incident light intensity on the focusing effect is explored. An exact formula is proposed to derive electric field E from electric flux density D in a Kerr-Dispersive medium. Surface plasmon (SPs) modes and Fabry-Perot (F-P) resonances are used to explain the physical origin of the light focusing phenomenon. Focused ion beam milling can be implemented to fabricate the proposed lens. It can find valuable potential applications in integrated optics and for tuning purposes.