Ne Laser Research Articles

Synthetic-wavelength self-mixing interferometry for displacement measurement

A simple synthetic-wavelength self-mixing interferometer is proposed for precision displacement measurement. Choosing the frequency difference of the orthogonally polarized dual frequency He–Ne laser appropriately, we introduce synthetic wavelength theory into self-mixing interference principle and demonstrate a feasible optical configuration by simply adjusting the optical design of self-mixing interferometer. The phase difference between the two orthogonally polarized feedback fringes is observed, and the tiny displacement of the object can be measured through the phase change of the synthetic signal. Since the virtual synthetic wavelength is 106 times larger than the operating wavelength, sub-nanometer displacement of the object can be obtained in millimeter criterion measurement without modulation, demodulation and complicated electrical circuits. Experimental results verifies the synthetic wavelength self-mixing interferometer's ability of measuring nanoscale displacement, which provides a potential approach for contactless precision displacement measurement in a number of scientific and industrial applications.

Anomalous Variation of Beat Frequency in a Dual Frequency He–Ne Laser**Supported by State Key Laboratory of Precision Measurement Technology and Instruments, Tsinghua University, under Grant No DL14-02.

The beat frequency in a dual frequency He–Ne laser varies while the resonant cavity length is tuned. As to the laser with two longitudinal modes, the variation amplitude is commonly less than 500 kHz, proven by experiments and theories. This study reveals an anomalous variation of the beat frequency when a piece of element is put into the cavity and is aligned with the laser axis. Consequently the variation amplitude could reach 22 MHz, several dozen times larger than that without the intra-cavity element. This cannot be explained only by laser mode pulling and pushing effects. Some influencing factors are investigated experimentally, including the tilted angle of the element and the distance between its surface and cavity mirror. The qualitative analysis is discussed, which agrees with the experimental results.

Nonlinear optical investigation of normal ovarian cells of animal and cancerous ovarian cells of human in-vitro

Laser-based study of two types of ovarian cells has been reported. For both normal and cancerous ovarian cells, growth and reproduction of cells formed to transparent and fresh substrates. Normal and cancerous cells fixed on glass substrate and nonlinear behavior of this microsize biolayer investigated by Z-scan technique using CW He–Ne laser. The magnitude and sign of nonlinear refractive index of normal and cancerous ovarian cells have been reported. Results show that nonlinear optical behavior of normal animal (Wistar rat) and cancerous human cells is different. Nonlinear refractive index (n2) of all studied normal biolayers has negative sign and vice versa for cancerous biolayers. Additionally magnitude of n2 for all samples was in order of 10−8 (cm2/w). So optical apparatus like Z-scan can be used for discriminate normal and cancerous ovarian cells and may be considered for optical diagnostic methods in medicine later.

Laser interference signal acquisition for Fourier transform spectrometer

The laser interference signal provides effective control signal for the reliable operation of atmospheric sounder. Main components of interferometer are presented by analyzing the principle of swinging interferometer in this paper. In order to acquire the laser interference signal, it is necessary to design a method of signal acquisition for the interferometer with analyzing the noise performance of the preamplifier. By means of an interference experiment of He–Ne laser, the sinusoidal signal is obtained, the frequency of which varies with change of angular velocity of moving mirrors. The experimental results indicate that the principle of swing interferometer is feasible, and that the method of interference signal acquisition is correct.

Investigation of acousto-optic properties of tellurium-based glasses for infrared applications

We examined the physical properties of infrared optical glasses composed of tellurium, germanium, selenium, sulfur and silicon. In particular, we measured optical, acoustic and photoelastic parameters of the following alloy compounds: germanium–selenium–tellurium (Ge–Se–Te), germanium–selenium–sulfur–tellurium (Ge–Se–S–Te), germanium–silicon–tellurium (Ge–Si–Te) and silicon–tellurium (Si–Te). Like single-crystal tellurium, the glasses demonstrate good acousto-optic (AO) diffraction efficiency and have reasonable optical transparency in a wide spectral region covering wavelengths from 1.5 to 20 μm. The optical, acoustic and photoelastic properties of the tellurium-based compounds were measured using infrared lamp sources of radiation as well as He–Ne and CO2 lasers. In this paper, we report on the optical, acoustic and photoelastic parameters of a selection of these compounds and discuss the advantages and disadvantages of using these glasses for AO device applications. We also present the measured characteristics of an AO cell fabricated in a Si20Te80 glass material which exhibited high optical uniformity and long-term chemical stability.

Investigation of Warpage Behavior of Silicon Semiconductor on a Silicon - Adhesive - Ceramic Integrated Structure at Cryogenic Temperatures--STUDENT BEST PAPER $1500

Silicon wafer is widely used as a base material for readout integrated circuit (ROIC) of infrared sensors. There is a heterogeneous component assembly with the silicon wafer material. Warpage behavior of silicon readout integrated circuit is dependent on the material properties and geometrical properties of the integrated materials. Warpage behavior of the silicon material directly affects the warpage of the sensor which must be operated at cryogenic temperatures (around 80 K). There exist a great difference between the operation and storage temperatures (~ 300 K) of these devices. When different materials with different thermal expansion coefficients are used such devices, thermal stresses develop on the components and surface deformations named as “warpage” are observed on the materials. The measurement of excessive thermal stress or warpage formation on the sensor is vital for reliability issues. In this study, warpage behavior of silicon material is examined in the temperature range from room temperature down to cryogenic temperatures (80 K) and under vacuum conditions less than 1 mTorr. The silicon ROIC is integrated on an alumina ceramic by applying an adhesive between these two layers. After the application of the adhesive material, the integration of the silicon to ceramic is accomplished using a pick and place equipment. The warpage of silicon wafer is measured by a Fizeau Laser Interferometer which uses a 633 nanometer wavelength He – Ne laser. The warpage of the diced silicon is measured before and after the integration to the ceramic so that the effect of curing process of the adhesive is determined after which, the warpage of the silicon material is measured at atmospheric pressure and also under vacuum conditions at room temperature. The warpage of silicon material on the integrated structure is measured with increments of 10 K for both cooling from room temperature to 80 K and heating from 80 K to room temperature. In order to reach cryogenic temperatures, a liquid nitrogen cooled vacuum envelope is utilized. The envelope has an optical flat (made of BK7 material and 2.35 mm thick) for interferometric measurements. There are a total of five integrated structures for the warpage measurements. At each of these structures, the silicon material thickness is different. Comparison of the warpage behavior of the silicon material for different thicknesses are performed. Thermal cycling between room temperature and 80 K is also performed up to 5 cycles for each of the integrated structures. Thermal cycling effect on silicon warpage is discussed for silicon - alumina - adhesive trimaterial assembly structure.

Photoluminescence, cathodoluminescence and micro-Raman investigations of monoclinic nanometre-sized Y2O3 and Y2O3:Eu3+

Herein we describe a large scale synthesis of nanosized, monoclinic Y2O3 and Y2O3:Eu3+ with 2 mol% Eu3+ in a plasma-discharge chamber.

Bulk growth, crystalline perfection and optical characteristics of inversely soluble lithium sulfate monohydrate single crystals grown by the conventional solvent evaporation and modified Sankaranarayanan–Ramasamy method

Good quality bulk size single crystals of inverse soluble lithium sulphate monohydrate (LSMH) have been grown by the modified Sankaranarayanan–Ramasamy (SR) method. A growth rate as high as 3 mm per day has been obtained for LSMH growth without substantially degrading the optical quality. The rocking curve recorded using the high resolution X-ray diffraction (HRXRD) technique reveals that the crystals grown by this method have a high degree of crystalline perfection. The optical quality of the crystals was studied using an UV-vis-NIR spectrum and the optical constants of the LSMH crystals were calculated. The laser damage threshold value of the grown crystals has been determined using a nanosecond Nd:YAG laser operating at 532 nm. Photoconductivity studies of the grown LSMH crystals reveal a positive photoconductivity behaviour of the grown crystals. The photoluminescence spectrum of the LSMH crystals shows a prominent emission peak at 373 nm. The third order non-linear optical properties of the LSMH crystals were investigated in detail by the Z-scan technique using a He–Ne laser operating at 632.8 nm. The non-linear refractive index (n2), non-linear absorption coefficient (β) and third order non-linear susceptibility (χ(3)) of the LSMH crystals were calculated.

Hematoporphyrin monomethyl ether combined with He–Ne laser irradiation-induced apoptosis in canine breast cancer cells through the mitochondrial pathway

Hematoporphyrin monomethyl ether (HMME) combined with He-Ne laser irradiation is a novel and promising photodynamic therapy (PDT)-induced apoptosis that can be applied in vitro on canine breast cancer cells. However, the exact pathway responsible for HMME-PDT in canine breast cancer cells remains unknown. CHMm cells morphology and apoptosis were analyzed using optical microscope, terminal deoxynucleotidyl transferase dUTP nick end labeling fluorescein staining and DNA ladder assays. Apoptotic pathway was further confirmed by Real-time-polymerase chain reaction and Western blotting assays. Our results showed that HMME-PDT induced significant changes in cell morphology, such as formation of cytoplasmic vacuoles and the gradual rounding of cells coupled with decreased size and detachment. DNA fragmentation and cell death was shown to occur in a time-dependent manner. Furthermore, HMME-PDT increased the activities of caspase-9 and caspase-3, and released cytochrome c from mitochondria into the cytoplasm. HMME-PDT also significantly increased both mRNA and protein levels of Bax and decreased P53 gene expression in a time-dependent manner, while the mRNA and protein expression of Bcl-2 were repressed. These alterations suggest that HMME-PDT induced CHMm cell apoptosis via the mitochondrial apoptosis pathway and had anti-canine breast cancer effects in vitro.

Inhibition Effect of a Laser on Thickness Increase of p-Type Porous Silicon in Electrochemical Anodizing

We demonstrate that the thickness increase of the porous layer on p-type (1–10 ohm-cm) silicon can be inhibited from hundreds to several nm/min in regular anodizing by exposure to He–Ne laser irradiation. During 2.0 mW laser irradiation, the growth in thickness was reduced to 5–6 nm/minute by anodizing with a current density of 10 mA/cm2. The inhibition effect on the thickness increase of porous silicon depends significantly on the laser power during a fixed anodizing time.

Studies of optical texture, birefringence, order parameter, normalized polarizability and validation of the four-parameter model of a thermotropic mesogen 7OAOB

Study of optical texture of different mesophases and phase transition temperatures of the liquid crystal compound 4,4′-di-n-heptyloxy-azoxy benzene has been carried out by using optical polarizing microscope. Enthalpy values and the phase transition temperatures have also been conducted by DSC studies. The variation of refractive indices with temperature has been measured by a thin prism technique using He–Ne laser and temperature dependent birefringence is calculated which shows a moderate value. Validation of the modified four-parameter model based on Vuks approximation has been carried out and reported in this article. The most important characteristics of LC compound namely macroscopic and microscopic order parameter have been evaluated by using direct extrapolation method and modified Vuks method based on Haller's extrapolation respectively. Temperature gradients of refractive indices have also been calculated. Further the normalized polarizabilities for extraordinary and ordinary rays and their ratio have been reported in this paper.

Erythrocyte aggregation under high pressure studied by laser photometry and mathematical analysis

The effects of hydrostatic pressure on erythrocyte aggregation have been studied by laser photometry and analysis based on a phenomenological theory. Samples were prepared by suspending swine erythrocytes in their own plasma. A high-pressure vessel consisting of a stainless-steel block with a hole to hold a sample cell and two sapphire windows to allows the passage of a He–Ne laser beam was used in the experimental setup. The suspension was stirred at 1500rpm to disperse the erythrocytes homogeneously. Immediately after reducing the stirring rate from 1500rpm to 300rpm, the transmitted light intensity (I) was recorded every 10ms under a high pressure of 40–200MPa. The value of I increased with time (t) owing to erythrocyte aggregation. From the phenomenological theory, the equation ΔI(t)=ΔIeq[1−e−Kt/(1−B(1−e−Kt))] was derived for the change in the transmitted light intensity (ΔI) due to erythrocyte aggregation, where ΔIeq is the transmitted light intensity in the steady state, K is a time constant and B is a constant that represents the ratio of the number of interaction sites on erythrocyte aggregates at time t to that in the steady state. The observed time courses of ΔI obtained at all pressures could be closely fitted to the theoretical equation. ΔIeq roughly increased with increasing pressure. On the other hand, K and B abruptly decreased above 120MPa. The growth rate of aggregates decreased above 120MPa. These results suggest a change in the mechanism of erythrocyte aggregation at approximately 120MPa. We discuss the physical meaning of the parameters.

Growth and characterization of semiorganic single crystal of bis-glycine manganese chloride

Semiorganic single crystals of bis-glycine manganese chloride (BGMC) of dimension 5×3×3mm3 were grown from aqueous solution by slow evaporation method at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by the single crystal X-ray diffraction studies. BGMC was subjected to FT-IR and FT-Raman spectral analyses. The lower cutoff wavelength observed from UV–vis–NIR transmittance spectrum is 271nm. The mechanical strength of the grown crystal was estimated using Vickers microhardness tester. The dielectric response of the grown crystal was analyzed at different temperatures in the frequency range from 50Hz to 2MHz. Thermal properties were investigated by thermogravimetric, differential thermal and differential scanning calorimetric analyses. Chemical etching study shows the distribution of etch figures of various shapes in the grown single crystal. The third order nonlinear optical properties of BGMC were investigated by Z-scan technique employing He–Ne laser radiation of wavelength at 632.8nm.

Effect of anti-parallel and twisted alignment techniques on various propertiesof polymer stabilised liquid crystal (PSLC) films

ABSTRACTThin composite films consisting of liquid crystal (LC) domains surrounded by polymer networks, termed as polymer stabilised liquid crystals (PSLCs), were prepared by photo-polymerisation of a pre-polymer dissolved in LC. Four composite films were prepared with different rubbing directions and with and without electric field during photo-polymerisation. Morphological characterisation carried our using a polarising optical microscope (POM) and a scanning electron microscope (SEM) reveal significant changes in LC domain morphology and associated polymer networks with the application of electric field during the fabrication of the films. The electro-optic (EO) properties of PSLC films placed between two crossed polarisers were studied using a He–Ne laser under an action of externally applied electric field. It was found that the PSLC film with twisted alignment and polymerised in the presence of electric field showed better EO properties than other films. Transmittance obtained by EO studies was verified with absorbance studies using a Ultraviolet-Visible spectrophotometer. The dielectric behaviour of PSLC films in the frequency range 20–20 MHz was investigated using a precision impedance analyser. The obtained data were modelled using Debye and Cole–Cole methods to calculate relaxation time and distribution parameter. The relaxation time calculated through the Cole–Cole model is in agreement with response time.

Optically operated linear electrooptical effect in δ-Bi1−xNdxB3O6/polymer composites

A novel type of laser operated polymer composites based on orthorhombic δ-Bi1−xNdxB3O6 powders (where x=0.025÷0.100) was prepared. The powders were synthesized by means of polymeric precursor method through the citrate way. They were analyzed using XRD, and HRTEM methods, then embedded into polyvinyl alcohol (PVA) photopolymer. During solidification the additional DC-electric field alignment was carried out. The composite films with thickness up to 0.4mm were studied using the Senarmont method at wavelength of CW He–Ne laser 633nm with simultaneous application of the DC-electric field at 50kHz frequency possessing rectangular symmetrical form. As a source of photoinducing beam we used polarized 1064nm Nd:YAG laser radiation and its power density was varied using a Glan prism polarizer. The linear electrooptical (EO) effect measurements were carried out during and after Nd:YAG laser treatment at different temperatures. The laser stimulated EO effect was explored versus the Nd3+ content and temperature. It was shown that the Nd3+ ion content plays the crucial role in the observed EO effect efficiency. The contribution of the piezo-electrical and piezo-optical phenomena as well as phonons in the observed effects is discussed.

Detection of Neisseria meningitidis using surface plasmon resonance based DNA biosensor

Herein, we report the development of a surface plasmon resonance (SPR) based biosensor for the detection of Neisseria meningitidis DNA employing Kretschmann configuration. Highly c-axis oriented ZnO thin film of thickness 200nm was deposited on gold coated glass prisms by RF sputtering technique. Single stranded probe DNA was immobilized on the surface of ZnO thin film by physical adsorption method. SPR reflectance curves were recorded as a function of incident angle of He–Ne laser beam using a laboratory assembled SPR setup. The prepared biosensor exhibits a linear response towards target meningitidis DNA over the concentration range from 10 to 180ng/μl with a high sensitivity of about 0.03°/(ng/μl) and a low limit of detection of 5ng/μl. The SPR biosensor demonstrated high specificity and long shelf life thus, pointing towards a promising application in the field of meningitidis diagnosis.

Gas-discharge He–Ne laser with a wavelength of 1.52 µm for telecommunications systems

Results of a detailed study of a gas-discharge He–Ne laser with a wavelength of 1.52 µm for telecommunications systems are reported. Some important parameters of the laser are measured, such as the laser beam divergence (M2), the laser power as a function of temperature, laser power stability, noise characteristics of laser radiation, etc. A possibility of laser microminiaturization is mentioned, which is of interest for its application under conditions of intense electromagnetic interference.

Dynamics of carrier recombination in a semiconductor laser structure

Carrier-recombination dynamics is studied by the method of optical orientation at room temperature in the active layer of a laser diode structure. The dependence of the degree of electron-spin orientation on the excitation density is attributed to saturation of the nonradiative-recombination channel. The time of electron capture at recombination centers is determined to be τ e = 5 × 10–9 s. The temperature of nonequilibrium electrons heated by a He–Ne laser is estimated.

Effects of He–Ne laser on Daphnia magna Straus manifested in subsequent generations

The effects of He–Ne laser irradiation (including visible laser light 632.8 nm in wavelength and an attendant electromagnetic field from the laser apparatus) on the fertility, newborn quality and linear dimensions of the body of Cladocera Daphnia magna Straus were determined. It is shown that the attendant electromagnetic field generated by the laser apparatus can have significant impact on the results of low-intensity laser therapy. The laser light exposure of daphnia to a dose range of 1.7–1300 mJ cm−2 stimulates the integral functions of the daphnia’s body. At the same time, the attendant electromagnetic field (72 mA m−1 in the frequency range of 0.02–20 kHz and 400 mA m−1 in the frequency range of 3–4 MHz) causes the appearance of quickly dying and/or abnormal newborn (up to a small percent) that has never been observed in the control. Anomalies of daphnia mainly consisted of swimming antenna pathologies. Moreover, under the influence of the attendant electromagnetic field on parental daphnia only, these anomalies appear even in several subsequent generations of newborn. The negative impact on daphnia disappears completely after the suppression of the attendant electromagnetic field to laboratory background level. It is shown that laser light can partially compensate the negative impact of the attendant electromagnetic field on Daphnia.

Temporal dispersion induced commercial laser in speckle free intense imaging

Coherent imaging suffers from speckle, which is basically some uncorrelated intensity distribution and bears no obvious relationship to the macroscopic properties of the object illuminated. Reducing the spatial coherence of the illuminating beam, usually improves the quality of imaging by paying the penalty for reducing intensity, and directionality as well. Here, we demonstrate an alternative way of resolving the speckle issue by inducing temporal dispersion onto the commercial He–Ne laser beam, devising with a dispersive slope available near to the edge of the 1-D organic photonic band gap Cholesteric Liquid Crystal (CLC).