Corner Cube Prism Research Articles

A Q-switched Ho:YAG spatial ring cavity laser with three corner cube prisms pumped by a 1908 nm fiber laser

We demonstrate a tri-corner cube Q-switched Ho:YAG spatial ring cavity laser, which was resonantly pumped by a 1908 nm fiber laser. The polarization state of the intracavity oscillating laser was adjusted by a half-wave plate, and a continuous s-polarized laser of 2.57 W at 2090.9 nm was obtained at a pump power of 18.5 W, corresponding to an optical-to-optical conversion efficiency of 13.9 % and a slope efficiency of 33.3 %. When the corner cube prism, which has the weakest anti-misalignment capability, was tilted vertically by 1° or horizontally by 0.92°, the laser could still output the laser. For Q-switched operation, the tri-corner cube Ho:YAG laser has a pulse energy of 9.86mJ and a pulse width of 178.8 ns at a repetition rate of 100 Hz. At the maximum output energy, the beam quality was Mx2 = 1.3, My2 = 1.2.

Three-Dimensional Nano-displacement Measurement by Four-Beam Laser Interferometry

A 3D nano-displacement measurement method, where the difference in phase between the beams in a four-beam laser interference is changed, is proposed. Simulation results demonstrate that the variation of phase difference causes the deviation of the interference pattern in the laser interference system. Based on this theory, we design and build a four-beam laser interference system. The corner cube prism in the optical path is shifted, and the phase of the beam is changed by applying different voltages to a piezoelectric stage. The phase difference is obtained by analyzing the lattice pattern with subpixel precision, and then the displacement is determined by correlation operation. The experimental measurement results are consistent with the theoretical analysis, thereby verifying the feasibility of this measurement method.

Two-dimensional grating interferometer with nanometer accuracy

A two-dimensional grating interferometer with the nanometer accuracy is proposed, which employs a transmissive two-dimensional diffraction grating and a corner cube prism in its optical configuration. The distinctive features of this optical path configuration are as follows: (i) Fourfold optical subdivision is achieved based on the principle of secondary diffraction, enhancing optical subdivision capability. (ii) The utilization of a corner cube prism configuration enables parallel retroreflection of diffracted light, facilitating ease of optical alignment. Utilizing a two-dimensional transmissive grating with a period of 4 µm (resulting in an optical signal period of 1 µm after fourfold optical subdivision), the two-dimensional grating interferometer achieves measurement resolutions better than 8 nm along the x and y directions. Within a 100 µm range, the grating displacement errors are superior to ±38 and ±36 nm. The repeatability (standard deviation of error) during a reciprocating motion with a 4 µm stroke is superior to 14 nm. The proposed two-dimensional grating interferometer enables nanoscale resolution measurements, showcasing notable linear measurement capabilities and repeatability. It finds potential applications in ultra-accuracy positioning and machining equipment. The utilization of gratings with smaller periods holds the promise of realizing picometer-level measurement potential.

Full-Range Static Method of Calibration for Laser Tracker

This paper focuses on the challenge of the inability to accurately calibrate the static measurement of a laser tracker across the full scale. To address this issue, this paper proposes to add a hollow corner cube prism on a 50 m high-precision composite guide rail to achieve a double-range measurement of the laser tracker. Data analysis indicated that, in the 77 m identical-directional double-range measurement experiment, the maximum indication error of a single-beam laser interferometer was −29.5 μm, and that of a triple-beam laser interferometer was 14.6 μm, and the measurement indication error was obviously small when the Abbe error was eliminated. The single-point repeatability of the tracker was 0.9 μm. In the 50 m identical-directional verification experiment, the results of the direct measurement outperformed those of the double-range measurement, and the indication errors under standard conditions were −4.0 μm and −8.9 μm, respectively. Overall, the method used in the experiment satisfies the requirements of the laser tracker. In terms of the identical-directional measurement, the measurement uncertainty of the tracker indication error is U ≈ 1.0 μm + 0.2L (k = 2) L = (0~77 m). The proposed method also provides insights for length measurements using other high-precision measuring instruments.

Distant RF field sensing with a passive Rydberg-atomic transducer

We combine a rubidium vapor cell with a corner-cube prism reflector to form a passive RF transducer, allowing the detection of microwave signals at a location distant from the active components required for atomic sensing. This compact transducer has no electrical components and is optically linked to an active base station by a pair of free-space laser beams that establish an electromagnetically induced transparency scenario. Microwave signals at the transducer location are imprinted onto an optical signal which is detected at the base station. Our sensing architecture with a remote standalone transducer unit adds important flexibility to Rydberg-atom based sensing technologies, which are currently subject to significant attention. We demonstrate a ∼30 m link with no particular effort and foresee significant future prospects of achieving a much larger separation between the transducer and the base station.

A single-longitudinal-mode Er:YAG laser and MOPA system based on the Faraday effect

We demonstrate a continuously operating Er:YAG single-longitudinal-mode laser and its amplifier with a corner cube retroreflector based on the Faraday effect. A maximum power of 1.02 W, the central wavelength of 1645.46 nm, Er:YAG single-longitudinal-mode laser with a line-width of 204 kHz has been realized. The slope efficiency is 9.38% and the beam quality factors M2 are 1.16, 1.05 in the × and y directions. Additionally, the single-longitudinal-mode laser is amplified to 1.86 W by the double-pass amplifier. The results indicate that the unidirectional operation ring laser in combination with the corner cube prism provides a 1.6 μm continuous-wave single-longitudinal-mode laser with high-power and stability.

P‐4.8: Unidirectional Observable Aero Signage Display Using Dye‐doped Corner Cube Prisms Which Enable to Make Transparent from Back Side

Suppose that you look Arabic numerals on transparent glass windows or in the air. Which does it mean ‘85’ or ‘28’? You end up watching the mirrored images when you view from back side. So let us make the mirrored image invisible. To solve mirrored image problems of an aero signage which means images are floating in the air, our research group has utilized dye‐doped prisms and total internal reflection in optics. You know that water is generally colorless and transparent but the water in a bath tub is little blue. The color changes depending on the depth of water. The deeper, the darker water becomes blue. This is the reason why some color is generated in the dye‐doped material. In 2021, we presented a unidirectional observable display using letterings made by intaglio printings for arranging dye‐doped tiny prisms on a glass window. You can watch these colored letterforms from front and transparent pixels from back. But this 2021 model has a little defect that colors are less vivid because of color generating mechanism by twice reflection in conventional optical prisms using transparent materials for making transparent from back side. In this paper, the authors show an aero signage display using dye‐doped corner cube prisms which can lengthen light paths in the prism by multi‐times reflections to avoid the semi‐transparent problem which means colors are not vivid.

Pulsed Er:YAG single corner cube ring cavity with variable output ratio

In this paper, a ring cavity of Er:YAG laser with a single corner cube prism is investigated. Due to the depolarization effect of the corner cube, the tunable output coupling ratio was 0.25% to 72.67% by changing the angle of the λ / 4 plate according to the calculation results of Jones matrix. An experiment for checking the anti-detuning performances of the single corner cube cavity was also carried out. The results indicated that the output power was stable at the rotating angles of <3.06 deg and 1.637 deg along the vertical and horizontal directions, respectively. Under continuous wave operation, a 5.4 W vertically-polarized laser of 1645.1 nm was acquired through double polarizers with the beam quality factors (M2) of 1.17 in the x direction and 1.42 in the y direction, and the slope efficiency was 45.47%. Additionally, under the condition of a pulse-repetition-frequency (PRF) of 200 Hz, the pump power of 29.04 W, a maximum pulse energy of 2.2 mJ was realized, and the minimum pulse width was 86 ns, leading to a peak power of 25.58 KW.

Q-Switched Anti-Misalignment Ho: YLF Ring Cavity Laser with Single Corner Cube Prism

Q-Switched Anti-Misalignment Ho: YLF Ring Cavity Laser with Single Corner Cube Prism

Special issue “optical communications, sensing, and laser applications”

Special issue “optical communications, sensing, and laser applications”

A 1 × 48 large‐scale multi‐mode fibre optical switch

A 1 × 48 large-scale multi-mode fibre (MMF) optical switch driven by a stepper motor is reported. The insertion loss is <1.42 dB, which can be further reduced to 1.02 dB after optimisation. With the employment of a corner cube prism in the optics, the device is characterised by good repeatability of <±0.01 dB. Meanwhile, the device has a fast response of <8 ms.

Research on 2 μm polarization maintaining laser cavity based on the depolarization characteristics of a corner cube prism

Based on the Jones matrix theory, a polarization maintaining 2 μm ring laser with a cavity structure of corner cube prisms (CCPs) is firstly presented in this paper. The changes of polarization state are simulated and coincide with the corresponding 2.06 μm experimental results for output beams after the CCP. Research results show that if the incident beam is circularly polarized or linearly polarized, the output beam will be generally elliptically polarized. Only when the polarization azimuths of linearly polarized incident beams are 16.06°, 43.94°, 46.06° and 73.94° can the linearly polarized output beams with different polarization azimuth angles be obtained. As such an incident beam passes through two CCPs arranged in the same way according to four specially reflection sequences (ACB and BCA, BCA and ACB, BAC and CAB, CAB and BAC) respectively, the polarization maintaining 2 μm laser can be realized. This work provides a reference basis for the design of a 2 μm corner cube ring cavity laser to realize the preservation of polarization state, which have practical significance to improve the output characteristics of 2 μm laser.

Stability analysis and experimental measurements of the corner cube prism solid-state laser

In order to study the stability of corner cube prism solid-state laser under the effect of thermal lens, the resonant equivalence cavity, resonant G-parameter and auxiliary parameter theories were used to model the corner cube prism solid-state lasers containing a thermal lens. The laser stability with resonant cavity length was analyzed. In a stable condition, the beam radius was analyzed with regards to the distance from one of the corner cube prisms to gain medium by calculating the beam radius at each position under the resonator G-parameter theory. On this basis, a V-structured solid-state laser, pumped by a semiconductor laser and two corner cube prisms as a resonant, was built. In consideration of the effect of thermal lens produced by the pumped beam, the experimental measurements of the beam radius at two corner cube prisms and the gain medium were made for the resonant cavity length during stable condition of the laser. The experimental measurements agreed well with the simulation results, and showed that the maximum cavity length depended on thermal lens focal length of the gain medium, variation pattern in the beam radius at the corner cube prism, relationship between cavity length and the beam radius.

Corner cube prism-enhanced photoacoustic spectroscopy based gas sensing

A corner cube prism-enhanced photoacoustic spectroscopy (PAS) based trace gas sensor was demonstrated for the first time. A corner cube prism was used to reflect the laser beam to pass through the photoacoustic (PA) cell for two times. With the enhanced absorption, the PAS signal had a 1.49 times improvement compared to the sensor system without the prism. A minimum detection limit (MDL) of 1.48 ppm for the detection of acetylene (C2H2) was obtained. Furthermore, corner cube prim has a merit that the reflected beam is always parallel to the incident beam. Therefore, the PAS signal was measured with different rotation and pitch angels of the prism. The measured results indicated that such sensor system had an excellent signal stability and therefore is advantageous for field application.

Gas sensor based on corner cube prisms

A gas sensor absorption cell was introduced which was made of two corner cube prisms. The stability and sensitivity of the cell were improved using the reflectivity character and the senseless to tilting of light beam. The transmission characteristics of light beam were analyzed with geometric optics. Moreover, the transmission equation of probing light and the measurement equation of the system at both single-wavelength and dual-wavelength were put forward, and a gas concentration detection system was constructed. It is concluded that the times <i>N</i> of probing light traveling back and forth in the cell is determined by the distance between axes of the two corner cube prisms, the sensitivity for differential optical absorption spectroscopy(DOAS) is proportional to the times <i>N</i>. The sensor was used to detect concentration of methane.The results show that the inspection threshold of the cell approaches 50 ppm for methane at <i>N</i> is 3.

Impact Response Measurement of Poly-Urethane Sheet Using an Optical Interferometer

[abstFig src='/00290003/16.jpg' width='300' text='The changes impact force to the sheet' ] A method for measuring the impact response of a polyurethane sheet is proposed. In the method, the velocity, acceleration, force, and displacement of a spherical body dropping onto the polyurethane sheet is measured using an optical interferometer. Only the velocity is measured from the Doppler shift of the laser light reflected on the cube corner prism embedded inside the spherical body. The optical center of the cube corner prism is made to coincide with the center of gravity of the whole spherical body to minimize the effect of the attitude change of the body. The acceleration, displacement, and inertial force of the body are calculated from the velocity. The dropping body is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 0.1 ms is estimated to be 0.23 N, which corresponds to 0.14% of the maximum force of approximately 1.60×102N. In the experiment, 10 drop measurements are conducted and show good reproducibility of this method.

Note: Optimal choice of the reflector by phase analysis for heterodyne interferometric roll angle measurement.

The choice of an actual reflector instead of an ideal or perfect reflector has to be dealt with for heterodyne-interferometric roll angle measurement methods. The candidates of regular reflectors such as corner cube prism and right angle prism are analyzed by the homogeneous coordinate transformation method, which provides a theoretical basis for the determination of the actual reflector. Furthermore, the influences of the phase loss of the determined reflector are strictly argued due to non-perfect or natural characteristics itself. Several tactics are considered to solve this problem by phase analysis. By contrast, it is an optimal choice that mirrors-based right angle prism can improve evidently the phase loss by experiment.

利用平凹透镜和标准角锥棱镜实现反射光束发散的方法

利用平凹透镜和标准角锥棱镜实现反射光束发散的方法

A high-precision roll angle measurement method

A novel high-precision measurement method for measuring roll is presented. The pentagonal prism and corner-cube prism are used as splitting element and sensitive element, respectively. A pair of parallel collimated beams generated by a pair of splitting pentagonal prisms is incident upon the target moving along linear guide. Two beams returning from two corner-cube prisms on the target reach two four-quadrant photoelectric detectors (QD1 and QD2), respectively. So the roll can be measured by differential measurement based on QD1 and QD2. Further, the measurement resolution can be doubled and resistance to common mode interference can be enhanced, by adopting common-path structure based on the polarization splitting prisms. Feasibility of the method is verified by theoretical analysis and experiments. When the system parameters apply to the values supposed, for the roll, the angular resolution can reach to 0.1″, and measuring accuracy is about 1″.

An optical straightness measurement sensor for the KRISS watt balance

We present an optical straightness measurement sensor applicable to the watt balance experiment. Key parts of the sensor are a cube-corner prism and a right angle reflector having a sharp edge. Beam reflected from the cube-corner prism is split into two opposite directions by the right angle reflector, and collected by photo detectors connected to a lock-in amplifier. Straightness error is measured by monitoring the normalized intensity difference of the two lock-in signals. We describe in detail about the implemented sensor and evaluated performance on its resolution, sensitivity, and nonlinearity comparing with a laser interferometer. Straightness measurement result of a translation stage agreed with that obtained by a laser interferometer within ±60nm over the measurement range of 40mm.