A high frame rate streak tube imaging lidar (STIL) for real-time 3D imaging of underwater targets is presented in this paper. The system uses 532nm pulse laser as the light source, the maximum repetition rate is 120Hz, and the pulse width is 8ns. LabVIEW platform is used in the system, the system control, synchronous image acquisition, 3D data processing and display are realized through PC. 3D imaging experiment of underwater target is carried out in a flume with attenuation coefficient of 0.2, and the images of different depth and different material targets are obtained, the imaging frame rate is 100Hz, and the maximum detection depth is 31m. For an underwater target with a distance of 22m, the high resolution 3D image real-time acquisition is realized with range resolution of 1cm and space resolution of 0.3cm, the spatial relationship of the targets can be clearly identified by the image. The experimental results show that STIL has a good application prospect in underwater terrain detection, underwater search and rescue, and other fields.
Method of homogenization of CO2 laser heating by means of metal gauze is researched theoretically and experimentally. Distribution of light-field of expanded beam passing through metal gauze was numerically calculated with diffractive optical theory and the conclusion is that method is effective, with comparing the results to the situation without metal gauze. Experimentally, using the 30W DC discharge laser as source and enlarging beam by concave lens, with and without metal gauze, beam intensity distributions in thermal paper were compared, meanwhile the experiments based on thermal imager were performed. The experimental result was compatible with theoretical calculation, and all these show that the homogeneity of CO2 laser heating could be enhanced by metal gauze.
Laser Induce Fluorescence (LIF) is a widely used new telemetry technology. It obtains information about oil spill and oil film thickness by analyzing the characteristics of stimulated fluorescence and has an important application in the field of rapid analysis of water composition. A set of LIF detection system for marine oil pollution is designed in this paper, which uses 355nm high-energy pulsed laser as the excitation light source. A high-sensitivity image intensifier is used in the detector. The upper machine sends a digital signal through a serial port to achieve nanoseconds range-gated width control for image intensifier. The target fluorescence spectrum image is displayed on the image intensifier by adjusting the delay time and the width of the pulse signal. The spectral image is coupled to CCD by lens imaging to achieve spectral display and data analysis function by computer. The system is used to detect the surface of the floating oil film in the distance of 25m to obtain the fluorescence spectra of different oil products respectively. The fluorescence spectra of oil products are obvious. The experimental results show that the system can realize high-precision long-range fluorescence detection and reflect the fluorescence characteristics of the target accurately, with broad application prospects in marine oil pollution identification and oil film thickness detection.
This paper presents a kind of miniature handheld laser fluorescence spectrometer, which integrates a laser emission system, a spectroscopic system, and a detection system into a volume of 100×50×20 mm3. A universal serial bus interface is connected to PC for data processing and spectrum display. The emitted laser wavelength is 405 nm. A spectral range is 400 to 760 nm and 2-nm optical resolution has been achieved. This spectrometer has the advantages of compact structure, small volume, high sensitivity, and low cost.
We present an optical receiving system for LIF lidar using a direct view spectrometer based on holographic grating prism. The proposed receiving optical system consists of receiving telescope, slit, collimating lens, holographic grating prism, objective lens and ICCD camera. The receiving optical system based on this dispersion structure can not only reduces the optical distortion to offer a high optical efficiency, but also has a more compact structure which is very suitable for spectral dispersion of remote target. The system adopted an intensifier coupled a CCD to make up an ICCD camera. Based on real-time background subtraction algorithm, 60fps fluorescence spectrum can be obtained in real time. System validation experiment uses a semiconductor laser as excitation source to illuminate oil target to radiate fluorescence at a distance of 30 m. The fluorescent signal is received by the set up LIF lidar receiving optical system, and clear spectrum image is obtained. The designed in-line, direct view configuration holographic grating prism spectrometer owns the advantages of high light throughput, less optical distortions, compact structure, small volume and easy operation, which make a practical portable receiving optical system.
In this paper, we present a prism spectrometer that exploits a double Amici prism dispersion structure. The system consists of a slit, a collimating lens, a double Amici prism, an imaging lens and a CCD. The incident light enter into slit, and then is paralleled by a collimating lens to the double Amici prism. The double Amici prism is used to realize spectral dispersion. The dispersed light is collected by an imaging lens and image on the photosensitive surface of the CCD. The dispersion resolution is theoretical analyzed from the ray tracing point of view. In addition, the imaging position on CCD element at different wavelength is presented according to nonlinear curve of dispersion. The designed prism spectrometer can obtain a high light throughput and less optical distortion spectrum in the spectral range of 370-700nm. In experiment, we measured the spectral resolution of the designed prism spectrometer at five wavelength used a grating monochromator. The designed in-line, direct view configuration prism spectrometer owns the advantages of high light throughput, less optical distortions, compact structure, small volume and easy operation, which has important role in application of laser spectral measurement especially laser remote sensing spectral detection.
A method using rotating Fabry–Perot (FP) mirror to measure CO2 laser wavelength was developed. The variation of FP transmittance changing with laser incident angle was calculated theoretically and the variation curve was given. The calculation illustrates that the variation of FP reflectance with incident angle 0 to 30 deg has little effect on the transmittance of FP. In the experiments, the CO2 laser transmittance variation of FP was measured at a wavelength of 9.27 μm. To improve the measurement precision of the laser wavelength, the method using the centrosymmetric peaks of FP transmittance curve in the range from −20 to +20 deg of laser incident angle was proposed. The precision of the measurement is about 0.01 μm. The experiment result is consistent with theoretical analysis, which demonstrates the feasibility of the laser wavelength measurement using rotating FP method.
Soliton decay and dispersive wave generation in photonic crystal fiber (PCF) are investigated. Grating-eliminated no-nonsense observation of ultrafast incident laser light e-fields technique is used to measure the temporal and spectral evolutions of soliton. Soliton decay and dispersive wave generation are clearly demonstrated. At low pump power, there is only soliton decay and no dispersive wave generated because all frequencies are in the anomalous dispersion region of the PCF, and the soliton spectrum does not touch the spectrum of linear dispersive waves. At relatively high power, a part of the soliton energy is transferred from soliton to a dispersive wave and falls on the blue side of the original carrier frequency of the incident pulse.
To provide high efficient pumping source for THz laser, we designed a new active frequency stabilized system for gain switched RF CO2 laser. According to our theoretical analysis and experimental study, the pulse setup time is varied for different output power. The pulse setup time is shortest when the output power is highest for a pulse laser. It is equivalent to stabilize the laser frequency and power if the pulse setup time is locked in the center of laser gain curve. By the method of adjusting the pulse setup time, we have stabilized a pulse rf excited CO2 laser at the center of the laser gain curve. The frequency stability is estimated to be less than 5MHz.
We designed a new solid-state laser with the construction of radial slab array. Three kinds of gain
distributions are considered according to different pumping structure. The numerical calculated results show
that this kind of laser can output high beam quality laser both coherent and incoherent conditions. It is
prospective to be a new research direction for high power, high beam quality, compact and scalable solid
Optic field intensities of double and triple parallel slabs solid laser are numerically calculated. The results show that high beam qualities are difficult to obtain no matter coherent or incoherent output. In order to obtain high beam quality for mult-slab solid laser, we designed a new solid laser construction of radial slabs array according to the present condition for solid and RF excited radial array CO2 gas laser. The numerical calculated results show that this kind of laser can output high beam quality laser both coherent and incoherent cases. It is prospective to be a new research direction for high power, high beam quality, compact and scale solid laser.
A tunable electro-optically Q-switched rf-excited partial Z-fold CO2 waveguide laser with two channels has been designed. Q-switched pulses were obtained from the partial Z-fold channel. The peak power is 730 W, and the pulse width is 150 ns. Cw laser output was obtained from the other channel, which can be tuned by a grating. A stable pulse heterodyne waveform and its Fourier transform (frequency spectrum) were also observed.
An experimental investigation of a pulsed electrooptically Q-switched radio-frequency partial Z-fold waveguide CO2 laser with two channels is presented. The heterodyne frequency stability is analyzed in theory. Q-switched pulses are obtained from the partial Z-fold channel. The peak power is 730W and the pulse width is 150 ns. CW laser can output from the single channel. The laser output directions are opposite.
Two kinds of Q-switched RF excited waveguide CO2 lasers using Q-switching and FM crystal respectively are studied. They are used to detect laser return signal from targets of 20m distances without using telescope in experiment. The waveform of pulse laser heterodyne and its frequency spectrum of Fourier transform scattered from targets are studied. According to radar distance equation, the laser can be applied to detect targets of 5Km distances using telescope.