Glan-Taylor Research Articles

Widely Tunable Narrow Linewidth Dual-Wavelength Yb-Doped Fiber Laser With Inhomogeneous Polarization Output

We demonstrate a widely tunable narrow linewidth dual-wavelength Yb-doped fiber laser with switchable inhomogeneous polarization output based on the Pancharatnam-Berry phase optical elements and volume Bragg grating experimentally. By rotating the Glan laser polarizer, we can obtain the switchable radially and azimuthally polarized beam with tunable wavelength separation ranging from 0.4 nm to 68.2 nm. The delivered spectrum shows excellent stability and linewidth narrower than 0.08 nm. Moreover, the polarization extinction ratio of the radially and azimuthally polarized beam can reach 94.2% and 93.6%, respectively. This tunable narrow linewidth dual-wavelength laser could enrich the manipulation potential of the fiber laser, and would benefit many applications like THz wave generation.

Polarization beam splitting in a Glan-Taylor prism based on dual effects of both birefringence and Goos-Hanchen shift

With the structure of biprism, polarization beam splitting in a Glan-Taylor polarizer was explored based on the birefringence and Goos-Hanchen shift. Due to the birefringence of the light in calcite crystal, the extraordinary light worked as the position calibration. As for the ordinary light, the propagated direction tilted noticeably due to the refraction as well as Goos-Hanchen effect at the prism-air interface of in the air gap. The Snell's law and stationary-phase approach were utilized for the calculation of the beam splitting between the two orthogonal polarization elements. By choosing appropriate incident angle and initial polarization, remarkable beam splitting was realized. With this configuration, the resolution with a magnitude of 10−5° and 10−3° was achieved for the response of the incident angle and polarization detection respectively.

Identification of Enantiomers Using Low-Frequency Raman Spectroscopy.

Distinguishing between d and l enantiomers is of important scientific interest, especially for the pharmaceutical industry. Enantiomeric differentiation in the solid form is repeatedly presented as a challenge in the research community. Raman spectroscopy is a nondestructive tool, widely used for the characterization of different materials by probing their vibrational modes. The low-frequency region of the Raman spectrum reveals lattice-level interactions and global fluctuations in the molecule. Lower frequencies correspond to vibrations arising from weaker bonds and long-range interactions and hence are very susceptible to polarization changes. This work presents low-frequency Raman (LFR) spectroscopy as a facile technique to identify enantiomers. The optical setup of conventional Raman spectroscopy is engineered such that the excitation and collection geometries use an asymmetrical focal cone. In addition, a half-wave retarder is added to the excitation path and a Glan-Taylor polarizer is added to the collection path, and these modifications allow us to select the polarization plane for both excitation and collection geometries. The asymmetry in the foci when using a polarized beam for excitation provides different intensities of the collected signal for each polarization plane. In a calibrated system, one can define the chirality of an analyte by comparing the intensity of the LFR signal along orthogonal sets of polarization planes. For nonchiral molecules, the spectral intensity is always higher in the co-polarized plane when compared to the orthogonally depolarized plane, as expected. This contrast in the intensity of Raman spectra serves as a distinct tool for identifying enantiomers.

TE/TM mode full-spatial decomposition of AlGaN-based deep ultraviolet light-emitting diodes

The full-spatial decomposition of transverse electric (TE)/transverse magnetic (TM) mode in AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) has been experimentally investigated by introducing self-built light intensity test system mainly composed of angle resolution bracket, Glan–Taylor prism and spectrometer. Through roughening the sapphire sidewall, the extraction efficiency of DUV-LED is improved, for both TE and TM mode light with no polarization selectivity. The introduction of self-built light intensity metrology system has been reflected via scribing the sapphire sidewalls using various laser conditions, which show a reliability in the enhancement validation of the light extraction efficiency. More importantly, the self-built light intensity test system enables effective feedback on epitaxial structures and chip structure design and provides a new perspective to design high efficiency AlGaN-based DUV-LEDs.

Manipulating longitudinal photonic spin Hall effect based on dynamic and Pancharatnam-Berry phase

Photonic spin Hall effect is generally described as a spin-dependent splitting. Previous studies have focused on the transverse spin-dependent splitting of light field. In this work, a method of manipulating the longitudinal photonic spin Hall effect which is based on dynamic and Pancharatnam-Berry phase is proposed. The theoretical analysis demonstrates that the lens group consisting of a Pancharatnam-Berry phase lens and a dynamic lens has two spin-dependent foci. Firstly, because Pancharatnam-Berry phase is spin-dependent, the left- and right-handed circularly polarized component can respectively acquire a Pancharatnam-Berry phase with opposite sign when a linearly polarized light beam passes through the Pancharatnam-Berry phase lens with phase retardation <inline-formula><tex-math id="M90">\begin{document}${\text{π}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20182004_M90.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20182004_M90.png"/></alternatives></inline-formula>. It leads one circularly polarized component to be focused and the other diverged. This is essentially the spin-dependent splitting of light field in momentum space, which is caused by Pancharatnam-Berry phase. And then, an ordinary lens is inserted behind the Pancharatnam-Berry phase lens to introduce a dynamic phase modulation. Due to dynamic phase being spin-independent, the constructed lens group can focus the photons with different spin states at different focal points longitudinally under the appropriate conditions. In other words, the lens group has two spin-dependent focal points. The two focal points split the photons with different spin states in the longitudinal direction. The longitudinal spin-dependent splitting is dependent on the focal lengths of the two lens and the distance between the two lenses. By changing the three parameters, arbitrary longitudinal spin-dependent splitting can be obtained. Lastly, an experimental system is set up to verify the theoretical results. The relationship between the spin-dependent splitting and the distance between the two lenses is measured. By introducing a Glan laser polarizer and a quarter wave-plate, the circularly polarized chirality of the light field at the focal point is also measured. These experimental results are all in good agreement with the theoretical analyses. These results are helpful in understanding the physical origin of photonic spin Hall effect and developing novel photonic devices based on photonic spin Hall effect.

Nonlinear frequency conversion and manipulation of vector beams.

Vector beams have been extensively investigated in recent years because of their fascinating vector character across the beam transverse section, which is demonstrated to be useful for optical micro-manipulation, optical micro-fabrication, optical communication, single molecule imaging, and so on. To date, it is still a challenge to realize nonlinear frequency conversion and manipulation of such vector beams because of the polarization sensitivity in most nonlinear processes. Here, for the first time, to the best of our knowledge, we generate second-harmonic vector beams by using three-wave mixing processes in our experiment, which occur in two orthogonally placed nonlinear crystals, and the vector property is recognized by using a Glan-Taylor polarizer. This nonlinear frequency conversion process enables vector beams to be obtained at new wavelengths, and opens up new possibilities for all-optical switching and manipulation of vector beams.

Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure

For the first time, an ultrahigh degree of optical polarization (DOP) of 81.8% in AlGaN-based deep ultraviolet LED (DUV-LED) operated at 286 nm has been experimentally demonstrated. The very high DOP was obtained by introducing the novel moth-eye microstructure fabricated on the backside of a sapphire substrate. Compared with conventional DUV-LED with a DOP of 64.7%, a significant 1.26-fold enhancement was obtained. It was worth mentioning that the DOP was accurately measured via self-built full spatial transverse electric (TE) and transverse magnetic (TM) mode light intensity test system, which was mainly composed of angle resolution bracket, Glan-Taylor prism, and spectrometer. For both TE and TM mode light, the extraction angle inside the semiconductor was extended from conventional (−26°, 26°), (−52°, −41°), (41°, 52°) to (−52°, 52°). Combined with finite difference time domain simulation, it was further confirmed that the novel moth-eye microstructure could notably weaken the total internal reflectio...

Influence of the optical axis orientation of the Glan-Taylor prism and the incident angle on the extraordinary ray

According to the propagation characteristic of the plane wave in the Glan-Taylor prism, using the method of the ray tracing, the deflection angle of the e-ray wave vector and its position on the exiting plane as a function of different parameters are calculated for the first time. In order to analyze the influences of the incident angle i together with the angle α of the optical axis of the Glan-Taylor prism and the crystal interface on the position of the extraordinary ray on the exiting plane L and L′, the variations of L and L′ with i and α are simulated, and the effects of α on L and L′ are very small except for i = 90°. To ensure the incident angle having no effects on the position of the e beam on the exiting plane, the incident angle should be controlled in a range of [0°,45°].

Compact static birefringent spectral range enhanced Fourier transform imaging spectrometer

A compact static birefringent spectral range enhanced Fourier transform imaging spectrometer (SEFTIS) is presented. The key component of the proposed SEFTIS is a new static dual-path birefringent interferometer formed by a polarizer, a Wollaston prism and a modified Glan–Taylor prism. Without any moving elements, it produces two independent interference patterns for two wavebands detections simultaneously, thereby providing at least twice the width of the original working spectral range. Compared with previous spectral range enhanced imaging spectrometers, the developed sensor highly reduces the complexity and alignment difficulty of the system. Theory and experimental prototype working in 400–1700 nm are described in detail.

Generation of multi-wavelength femtosecond laser pulse based on nonlinear propagation of high peak power ultrashort laser pulse in single-mode fiber and spectral selectivity technology

Highly-integrated high-reliability widely-tunable femtosecond laser sources have important application values in various research and application fields, such as ultrafast spectroscopy, quantum optics, remote sensing and bio-imaging. In multi-photon excited fluorescence microscopy, femtosecond laser sources with moderate pulse energy and wide wavelength tunable range can not only meet the application requirements of the different tissue structures for the peak power and excitation wavelength, but also improve the nonlinear fluorescence efficiency and imaging resolution of the sample, and thus enhancing the penetration depth. Considering the extensive application prospect and important scientific research significance of the widely tunable femtosecond laser, in this paper we conduct an experimental research of the high repetition rate multi-wavelength femtosecond laser generation in compact sized and low-cost configuration based on the nonlinear propagation scheme of the high peak power femtosecond laser pulses in single-mode fiber. In experiment, we first construct a highly-integrated reliable all-polarization-maintaining fiber femtosecond laser amplifier, which mainly consists of an environmentally stable all-polarization-maintaining fiber mode-locked laser oscillator, single-mode fiber stretcher, a single-mode power pre-amplifier, a dual-cladding Yb-fiber amplifier, and transmission grating-pair compressor. Self-starting mode-locked operation is assured with a semiconductor saturable absorber mirror, and intra-cavity dispersion compensation is realized by a chirped fiber Bragg grating in the mode-locked oscillator. The mode-locked oscillator, which delivers laser pulses with center wavelength peaked at 1035 nm, is robust operation as temperature changes from 10℃ to 40℃ and the measured power fluctuation is less than 1% RMS over 168 hours at 23℃. The amplified high repetition rate laser pulses are compressed in a double-pass 1000 lines/mm transmission grating-pair compressor. After compression, laser pulses with 5.83 W average power and 264 fs pulse duration at 34 MHz repetition rate can be obtained. Simultaneously, we also study the dependence of the compressed pulse duration on the amplified output power. Employing a home-made high reliable compact sized all-polarization-maintaining fiber femtosecond laser as a pump source and low-cost single-mode fiber as a nonlinear medium, the generation technology of the widely tunable femtosecond laser in only fiber format is also studied based on the self-phase modulation nonlinear spectral broadening mechanism. Simultaneously, in order to reduce the effect of the dispersion on the spectral broadening as much as possible, an 80-mm-long fiber is used in experiment. The used single-mode spectral broadening fiber has a 6-m-diameter core and 20 fs2/mm dispersion coefficient. By coupling the femtosecond pump laser pulses into the 6-m-diameter fiber core, the output spectrum presents a significant nonlinear broadening. The coupled pump power can be continuously adjusted by a combination of a half-wave plate and a Glan laser polarizer. After bandpass filtering the leftmost and rightmost spectral lobes in self-phase modulation and self-steeping induced broadened spectrum with bandpass filters centered at 980, 1000, 1050, 1070 and 1100 nm, the laser pulses with 203, 195, 196, 187, and 194 fs pulse duration can be obtained at the corresponding center wavelengths. The experimental scheme presented in this paper, which is based on the nonlinear spectral broadening of the highreliability femtosecond laser pulse in single-mode fiber and the spectral selectivity technology, provides a new research approach to the realization of the highly-compacted reliable widely-tunable femtosecond laser sources and has important research significance.

Switchable phase and polarization singular beams generation using dielectric metasurfaces

Singular beams which possess helical phase wavefront or spatially inhomogeneous polarization provide new freedom for optical field manipulation. However, conventional schemes to produce the singular beams have difficulty in realizing the flexible switch between different singular beams. In this work, we have experimentally demonstrated the capability of dielectric metasurfaces to generate three types of singular beams and switch between them at working wavelength of 1550 nm. We have shown vortex beam and cylindrical vector beam generation with single metasurface and cylindrical vector vortex beam generation with two cascaded metasurfaces. Moreover, experimental demonstration on switching cylindrical vector beam into vortex beam has also been done by combining one quarter-wave plate and a Glan laser polarizer. The experimental results match well with the analysis from the Jones matrix calculations. The average conversion efficiency of cylindrical vector beam to vortex beam was estimated to be 47.7%, which was about 2.3% lower than the theoretical prediction.

Linear stokes imaging spectropolarimeter based on the static polarization interference imaging spectrometer

The theoretical operation and experimental demonstration of a Fourier-transform linear imaging spectropolarimeter are presented. It is composed of a rotating Glan-Taylor prism and a Fourier-transform spectrometer based on Savart polariscope. The polarized light enters the spectrometer to create three sets of interferograms, where the spectral linear Stokes parameters can be calculated and acquired. Compared with previous instruments, the significant advantages of the described sensor are that there are no spatial aliasing in the polarized spectra and it can be used in wider spectral coverage with low cost, ultra-compact size and a simpler common-path configuration. Another static linearly Stokes imaging spectropolarimeter based on the field of view division technique and SPIIS is conceptually described. The spectral dependence of linear Stokes parameters can be recovered with Fourier transformation. Since there is no rotating or moving parts, the system is relatively robust.

Top-Seeded Solution Growth and Optical Properties of Deep-UV Birefringent Crystal Ba2Ca(B3O6)2

Single crystals of the birefringent material Ba2Ca(B3O6)2 (BCBO) with dimensions up to 40 × 28 × 10 mm3 were successfully grown by top-seeded solution growth (TSSG) method from B2O3–NaF flux. It exhibits high transmittance in the range of 190–3000 nm with UV cutoff of 178 nm, which is much shorter than that (189 nm) of the commercial UV birefringent crystal, the high-temperature phase of BaB2O4 (α-BBO). Meanwhile, BCBO crystal has large birefringence (Δn = no – ne = 0.2524–0.0862) in the wavelength range from 178 to 3000 nm and without phase transition from room temperature to the melting point. A prototype of Glan–Taylor polarizer made from BCBO crystal showed an optical extinction ratio of 104:1, which is comparable to those of commercial birefringence crystals. The experimental results demonstrate that the BCBO crystal can be a new promising birefringent crystal for UV, especially the sub-200 nm deep-UV range.

Wavelength-locked vectorial fiber laser manipulated by Pancharatnam-Berry phase.

We report a wavelength-locked cladding-pumped ytterbium-doped fiber laser that can simultaneously emit radially and azimuthally polarized beams based on Pancharatnam-Berry phase optical elements. Multi-wavelength free running operation of the radially and azimuthally polarized laser beams can be switched to a single-wavelength one assisted by volume Bragg grating, with wavelength locked at around 1053.4 nm and spectral linewidth of 0.06 nm (FWHW). By rotating the glan-taylor polarizer, we can obtain switchable radially and azimuthally polarized beams output. The radially and azimuthally polarized beams mode purity can maintain 97.3% and 96.3% at maximum output power, and the polarization extinction ratio (PER) can reach 97.8% and 95.9% for the radially and azimuthally polarized laser, respectively.

Exact and near backscattering measurements of the linear depolarisation ratio of various ice crystal habits generated in a laboratory cloud chamber

Ice clouds were generated in the Manchester Ice Cloud Chamber (MICC), and the backscattering linear depolarisation ratio, δ, was measured for a variety of habits. To create an assortment of particle morphologies, the humidity in the chamber was varied throughout each experiment, resulting in a range of habits from the pristine to the complex. This technique was repeated at three temperatures: −7°C, −15°C and −30°C, in order to produce both solid and hollow columns, plates, sectored plates and dendrites. A linearly polarised 532nm continuous wave diode laser was directed through a section of the cloud using a non-polarising 50:50 beam splitter. Measurements of the scattered light were taken at 178°, 179° and 180°, using a Glan–Taylor prism to separate the co- and cross-polarised components. The intensities of these components were measured using two amplified photodetectors and the ratio of the cross- to co-polarised intensities was measured to find the linear depolarisation ratio. In general, it was found that Ray Tracing over-predicts the linear depolarisation ratio. However, by creating more accurate particle models which better represent the internal structure of ice particles, discrepancies between measured and modelled results (based on Ray Tracing) were reduced.

Spin-orbit interaction of light in metasuface

Spin-orbit interaction of light in metasurface is investigated in this paper. We theoretically analyze the transfromation of circularly and linearly polarized light by metasurface with Jones matrix. The results indicate that the interaction of light with spatially inhomogeneous and anisotropic metasurface leads to a coupling of spin-orbital angular momentum. The nanostructrues of metasurfaces are arranged at a definite rate of rotation, which induces an additional space-variant geometrical phase (i.e., Pancharatnam-Berry phase). The Pancharatnam-Berry phase is dependent on the polarization handedness of the incident wave. This characteristic can result in spin-dependent split. A left/right-circular polarized beam is transfromed into a right/left-circular polarized vortex beam by the metasurfaces. In the convertion process, the sign of spin angular momentum of photons is inversed. At the same time, each photon can acquire orbital angular momentum from the inhomogeneous and anisotropic media. The case that a linearly polarized beam inputs the metasurfaces also is considered. A linearly polarized wave can be regarded as the linear superposition of left-circular and right-circular polarized wave. The two circularly plarized components are respectively converted into circularly polarized vortex beam with reverse polarization handedness. The coherent superposition of the two output components forms a cylindrical vector beam. Finally, we adopt the combination of a metasurface and spiral phase plate to verify the theoretical results. The vortex phase can be eliminated by the spiral phase plate when a left-circular polarized light is input, while topological charge of vortex phase will increase when a right-circular polarized light is input. For the case of inputting linearly polarized beam, one of the two outputing circularly polarized components can be eliminated by the helical phase through using the spiral phase plate, while the topological charge of another component increases. It results in the fact that the intensity pattern splits into two parts. The central part does not have helical phase, while the ambient ring-shaped intensity has helical phase. In order to judge the polarization handedness of output wave, the Stokes parameter S3 is measured by inserting a Glan laser polarizer and a quarter wave plate behind the spiral phase plate. The experimental results are in good agreement with theoretical analyses. These results are helpful for understanding the manipulation of light with metasurface.

A promising birefringent crystal Ba2Na3(B3O6)2F

Bulk crystals of Ba2Na3(B3O6)2F (BNBF) have been successfully grown by top-seeded solution growth (TSSG) technique. Its transmittance spectra show a wide transparency range from 186nm to 3000nm. The refractive indices in 13 wavelengths were measured with high accuracy and the Sellmeier equations were obtained, which demonstrated that the title crystal displayed a birefringence (Δn=0.1030 at 588nm) comparable to that of the commercial birefringent crystal α-BBO (the high temperature form of BaB2O4). A prototype Glan-Taylor polarizer made of BNBF prisms was fabricated, which showed high transparency and large optical extinction ratio similar to the commercial polarizer made of α-BBO. In addition, BNBF crystal is less moisture sensitive than that of α-BBO, thus BNBF can be a potential new birefringent crystal.

Simultaneous Raman and laser-induced breakdown spectroscopy by a single setup

A new experimental configuration is introduced for simultaneous recording of Raman and laser-induced breakdown spectroscopy (LIBS) in a single spectrum. A laser pulse is divided into two beams by a Glan–Taylor prism. By focusing one beam to the sample surface, micro-plasma is created and LIBS signal is emitted. The other beam is directed to the same point of the sample, but does not focused. The scattered light due to the second laser beam is mixed with the plasma emission and is recorded in a single spectrum. Atomic and molecular spectra of some minerals and chemical samples are recorded by the mentioned setup. Due to the high-plasma quenching in liquids, LIBS signals are not detected for organic liquid samples, instead a strong stimulated Raman signal is appeared, and as a result, an overlay of ordinary Raman with stimulated Raman is observed.

The polarization-difference interference imaging spectrometer-Ⅱ. optical design and analysis

The static polarization-difference interference imaging spectrometer, based on the combination of Wollaston prism and Savart polariscope, can simultaneously acquire hyperspectral images for orthogonal polarization components. Optical specifications are determined according to the principle of interference spectroscopy and the technical parameters of an actual detector. A design scheme is demonstrated. The Savart polariscope, Wollaston prism and Glan-Taylor prism are designed according to the birefringent features of uniaxial crystal and the wave normal tracing. More emphasis is put on the influences of the dispersion of uniaxial crystal on the incident angle, thickness, and apex angle. This research can provide a theoretical guide in the engineering of the polarization-difference interference imaging spectrometer.

偏振干涉成像光谱仪中的格兰泰勒棱镜透射比

偏振干涉成像光谱仪中的格兰泰勒棱镜透射比