Double Wavelength Laser Research Articles

Surface Vertical Multi-Emission Laser with Distributed Bragg Reflector Feedback from CsPbI3 Quantum Dots.

Quantum dots (QDs) laser has become an important way to solve micro-application problems in many fields. However, single wavelength distributed Bragg reflector (DBR) has many limitations in practical applications, such as signal transmission. How to realize multiwavelength DBR lasing output simply is a challenge. To achieve a stable multi-wavelength quantum dots laser in the near-infrared region, the perovskite CsPbI3 QDs laser with DBR structure is developed in this paper. A tetragonal crystal structure with complete bonding information and no defect is explained by X-ray diffractions (XRD) and Raman spectrum. The cross-section morphology of the DBR laser and the surface morphology of QDs is measured by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. An elliptical light propagation field and a double wavelength laser radiation are obtained from the finite-difference time-domain (FDTD) simulation. The output of the three wavelength lasers at 770 nm, 823 nm, and 873 nm is measured. The emission time of a DBR laser is about 2 h, and the average fluorescence quantum yield is 60%. The cavity length selection and energy level model are put in place to clearly see the working mechanism. All the results suggest that an effective and stable CsPbI3 quantum dots DBR laser is realized.

Dental implant surface morphology, chemical composition, and topography following double wavelength (2780/940 nm) laser irradiation. An in vitro study.

The aim of this in vitro study was to evaluate morphology alterations, chemical composition, and topography of moderately rough dental implants following double-wavelength laser irradiation. Commercial-grade titanium dental implants representing different surface characteristics (Osseospeed [OS], TiUnite [TiU], and Roxolid SLActive [RS]) were used. Laser irradiation was performed using a computer-controlled robotic device with calibrated energy/power settings and deionized water spray. Micro-, nano-morphology surface alterations, chemical composition, and surface topography (Sa , Sds , Sdr ) in the test group (laser plus water), control group A (water only), and control group B (no treatment) were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and white light laser profilometer (Interferometry). SEM-evaluation revealed minor between-group differences in micro- and nano-morphology within each implant system. Significant overall differences in surface element content were observed between the test and control group B for all implant systems (p < .05). For the test compared with control group B, statistically significantly higher oxygen content was detected for OS and RS (p < .05), a corresponding significant difference was detected for carbon for TiU (p < .05). For RS, a significantly lower content of titanium and zirconium was detected within the test group (p < .05). A significant difference in topography between test and control group B was observed for OS (Sa : p = .039 and Sdr : p = .041) with the highest roughness value for control group B. Altered chemical composition and surface topography were observed for all implant surfaces compared with untreated control following double wavelength laser irradiation. A clinical evaluation of the impact of the altered surface composition following double wavelength laser irradiation on the ability to reosseointegrate appears warranted.

Double-wavelength coherent perfect absorption laser in Thue-Morse PT-symmetric photonic crystals

Coherent perfect absorption laser points (CPA-LPs) are investigated in the Thue-Morse (Th-M) PT-symmetric photonic crystals. CPA-LPs are induced as incident light impinges perpendicularly upon the structure. The operating wavelengths of the CPA-LPs are dependent on the Th-M sequence number, the incident angle and the gain-loss factor of materials. Especially, two CPA-LPs may be achieved with the same value of incident angle for a specific gain-loss factor. Double-wavelength laser consequently is supported in this structure and the corresponding transmittance of the CPA-LPs is optional. An abrupt jump in the calculated reflection coefficient phase could be found at the CPA-LPs as well. This study may be helpful in potential applications for lasers and highly sensitive sensors.

Dental implant surface temperatures following double wavelength (2780/940 nm) laser irradiation in vitro.

ObjectiveTo estimate the implant surface temperature at titanium dental implants during calibrated irradiation using double wavelength laser.Material and methodsA double wavelength laser, 2780 nm Er,Cr:YSGG and 940 nm diode, was calibrated and used to irradiate pristine titanium dental implants, OsseoSpeed, TiUnite and Roxolid SLActive, representing different surface modifications. Initial calibration (21 implants; 7 implants/group) intended to identify optimal wavelength/specific output power/energy that not critically increased the temperature or altered the micro‐texture of the implant surface. Subsequent experimental study (30 implants; 10 implants/group) evaluated implant surface temperature changes over 190 s. Irradiation using a computerized robotic setup.ResultsBased on the initial calibration, the following output powers/energies were employed: Er,Cr:YSGG laser 18.4 mJ/pulse (7.3 J/cm2)–36.2 mJ/pulse (14.4 J/cm2) depending on implant surface; diode laser 3.3 W (1321.0 W/cm2). During double wavelength irradiation, implant surface temperatures dropped over the first 20 s from baseline 37°C to mean temperatures ranging between 25.7 and 26.3°C. Differences in mean temperatures between OsseoSpeed and TiUnite implants were statistically significant (p < 0.001). After the initial 20 s, mean temperatures continued to decrease for all implant surfaces. The decrease was significantly greater for TiUnite and Roxolid SLActive compared with OsseoSpeed implants (p < 0.001).ConclusionCalibrated double wavelength laser irradiation did not critically influence the implant surface temperature. During laser irradiation the temperature decreased rapidly to steady‐state levels, close to the water/air‐spray temperature.

Abstracts from the 7th Congress of the World Federation for Laser in Dentistry European Division June 20–22, 2019 Parma, Italy

Abstracts from the 7th Congress of the World Federation for Laser in Dentistry European Division June 20–22, 2019 Parma, Italy

Rationale for using a double-wavelength (940 nm + 2780 nm) laser in endodontics: literature overview and proof-of-concept

The goal of endodontic research is to report interventions, techniques or protocols that are most likely to deliver the outcomes that are of most interest to both clinicians and patients. The development of a double-wavelength laser delivered concomitantly and through the same radial firing tip (RFT) may provide a unique combination of beneficial properties that may clinically surpass all previously reported laser-assisted protocols. The aim is to present a rational literature overview that could support the adoption of simultaneous use 2780 and 940 nm wavelengths for smear layer removal and disinfection respectively. In order to provide relevant clinical data, two distinct clinical cases of relatively high endodontic complexity are reported with 1-year follow-up. The results of both clinical cases show the immediate remission of symptoms, absence of clinical complications and complete radiographic healing. Together with the available amount of literature that could support the effectiveness of these two wavelengths to remove SL and to achieve deep dentin disinfection, it is possible to expect that this innovative combination of lasers delivered by RFT may be of high clinical relevance in the near future.

Study on dynamic deformation synchronized measurement technology of double-layer liquid surfaces

Accurate measurement of the dynamic deformation of double-layer liquid surfaces plays an important role in many fields, such as fluid mechanics, biomechanics, petrochemical industry and aerospace engineering. It is difficult to measure dynamic deformation of double-layer liquid surfaces synchronously for traditional methods. In this paper, a novel and effective method for full-field static and dynamic deformation measurement of double-layer liquid surfaces has been developed, that is wavefront distortion of double-wavelength transmission light with geometric phase analysis (GPA) method. Double wavelength lattice patterns used here are produced by two techniques, one is by double wavelength laser, and the other is by liquid crystal display (LCD). The techniques combine the characteristics such as high transparency, low reflectivity and fluidity of liquid. Two color lattice patterns produced by laser and LCD were adjusted at a certain angle through the tested double-layer liquid surfaces simultaneously. On the basis of the refractive indexes difference of two transmitted lights, the double-layer liquid surfaces were decoupled with GPA method. Combined with the derived relationship between phase variation of transmission-lattice patterns and out-of plane heights of two surfaces, as well as considering the height curves of the liquid level, the double-layer liquid surfaces can be reconstructed successfully. Compared with the traditional measurement method, the developed method not only has the common advantages of the optical measurement methods, such as high-precision, full-field and non-contact, but also simple, low cost and easy to set up.

Local phase-structure modification inside of lithium silicate glass by combined double-wavelength laser action

The process of local structure modification inside of lithium silicate glass under the combined laser action of two different wavelengths is considered. The first step is laser irradiation of ultrashort laser pulses with 532 nm wavelength, which is used to create of nucleation centers inside of the optically transparent glass. The crystallization of the structural modification areas was carried out by a photothermal action of CO2 laser radiation with a 10.6 μm wavelength. The range of crystallization temperatures was defined and the kinetics of the phase transformations of the modified regions inside of the glass were studied. Duration of crystallization was about 10 min with a slow heating and 25 s at the fast heating to crystallization temperature.

A switchable dual-wavelength erbium-doped fiber laser based on Sagnac loop inserted with two FBGs

A novel switchable dual-wavelength erbium-doped fiber (EDF) laser is demonstrated. The wavelength selection element consists of two fiber Bragg gratings (FBGs), a polarization controller (PC) and a 3 dB coupler forming a Sagnac loop inserted with two FBGs. We study the effect of coupling ratio on filtering performance in this paper. By adjusting PC, we can change the wavelength-dependent loss, and then using nonlinear polarization rotation effect to suppress the mode competition caused by the homogeneous broadening of EDF, we obtain single- and double-wavelength laser outputs. At room temperature, under 200 mW pump power, dual-wavelength laser is achieved, and the center wavelengths are 1545.34 nm and 1548.20 nm, respectively. The peak power values are −13.36 dBm and −14.58 dBm, and side mode suppression ratios (SMSRs) are 41.10 dB and 39.88 dB, respectively. Within two hours, the maximum fluctuation of peak power is less than 0.7 dB, which shows that the demonstrated fiber laser is stable. Moreover, by adjusting PC, singel-wavelength laser output is obtained, the peak power is −6.27 dBm or −5.45 dBm, and SMSR is 40.03 dB or 39.96 dB at 1545.34 nm or 1548.20 nm, respectively.

Research on Intelligentized Recognition Technology for Double Wavelength Laser Measurement of Thin Film Thickness

Interference image processing is the key technology of optical interference measurement. This paper introduced the problems on automatic interference fringe processing in absolutely measurement based on laser interference, digital image processing technology. The image acquisition of the SiO2 film and the pre-processing of interferogram was performed.Decimal part of the interference fringes is obtained. Using high-resolution image acquisition system and computer reads and processes the interference image, replaces the traditional work of skilled workers of high intensity for a long time and improves the film thickness measurement accuracy.

双波段激光防护红外减反膜的研制

双波段激光防护红外减反膜的研制

双波段激光防护红外减反膜的研制

双波段激光防护红外减反膜的研制

双波段激光防护红外减反膜的研制

双波段激光防护红外减反膜的研制

Visualisation of the distributions of melanin and indocyanine green in biological tissues

A double-wavelength laser scanning microphotometer with the high spectral and spatial resolutions is developed for studying the distribution of endogenic and exogenic dyes in biological tissues. Samples of hair and skin biopsy with hair follicles stained with indocyanine green are studied. The spatial distribution of indocyanine green and melanin in the biological tissue is determined from the measured optical transmittance.

Venoarteriolar response to experimental venous hypertension in legs with chronic venous insufficiency and in healthy legs, measured using a double-wavelength laser Doppler technique.

The venoarteriolar response (VAR) of the skin in legs caused by experimental venous hypertension was measured using a new, double-wavelength laser Doppler probe technique (543 nm and 780 nm). This enables the measurement of the laser Doppler flux in the superficial and deep layers of the skin simultaneously. The recordings were obtained from the leg with the patient in a recumbent position with a sphygmomanometer cuff around the thigh. The VAR was recorded at the cuff pressures of 30 mmHg and 60 mmHg. Ten patients with chronic venous insufficiency (CVI) and 20 control subjects with healthy legs were investigated. The VAR increased in relation to the increase of cuff pressure at both wavelengths. There were no significant differences in the VAR between the cuff pressures within or between the legs with CVI and healthy legs. The VAR measured at 780 nm was very significantly greater than the VAR measured at 543 nm in legs with CVI (p<0.005), as well as in healthy legs (p<0.001). The VAR depends both on the wavelength of the laser Doppler light used and on the degree of venous hypertension. The VAR is not impaired in legs with CVI compared with healthy legs.

Blood flux and venoarteriolar response of the skin in legs with chronic venous insufficiency measured at two different depths by using a double-wavelength laser Doppler technique.

The laser Doppler flux (LDF) and the venoarteriolar response (VAR) of the skin in legs with chronic venous insufficiency (CVI) was measured by using a new double-wavelength probe technique (543 nm and 780 nm). The recordings were taken in a recumbent and in a sitting position. Ten patients with CVI and 20 control subjects with healthy legs were investigated. The LDF was found to be significantly enhanced in a recumbent position at 543 nm and in a sitting position at 780 nm in legs with CVI compared with healthy legs (P<0.05 and P=0.02, respectively). The authors could not find the VAR to be impaired in either wavelength in legs with CVI compared with healthy legs. The double-wavelength probe technique makes it possible to record simultaneously the LDF in the superficial and deep layers of the skin on the same place in the leg.

Computer code long path method for long path differential-absorption predictions using CO2 laser lines

A computer program LPM (Long Path Method) has been developed for imitative modeling of the concentration at gases (H2O, CO2, O3, NH3, C2H4) in the atmosphere using a long-path double-wavelength laser system equipped with two tunable CO2 lasers. The model is designed for four different lasing isotopes of CO2 (12C16O2, 13C16O2, 12C18O2, 13C18O2). The program determines optimal pairs of CO2 laser wavelengths, and the gas concentration retrieval errors from sounding data caused both by detector noise and systematic inaccuracy. The program was written in MS FORTRAN and Visual Basic languages for Windows 3.1 and an IBM-compatible PC. © 1995 American Institute of Physics.

Double-wavelength laser array with InGaAsP/InGaAsP multiple quantum well grown by Ar ion laser-assisted metalorganic molecular beam epitaxy

This letter reports a laser diode array of InGaAsP/InGaAsP multiple quantum well (MQW) lasers, emitting at different wavelengths, grown by Ar ion laser assisted metalorganic molecular beam epitaxy. A separate confinement heterostructure MQW laser film was locally irradiated during well growth with an Ar ion laser and processed into a laser diode array having a 6 μm stripe width and 300 μm pitch. The laser diode with an irradiated MQW active layer operated at 1.40 μm; the laser diodes with nonirradiated MQW active layers operated at 1.28 μm. The threshold currents of the 300 μm-long laser diodes were 23 mA for the irradiated diode and 55 mA for the nonirradiated diodes.

A double wavelength laser Doppler system to investigate skin microcirculation.

A new experimental laser Doppler setup has been designed to discriminate between total and superficial skin blood flow. This selectivity is based on the use of two wavelengths with different penetration depths into the skin. An argon ion and helium-neon laser are mounted on the same optical bench and are stabilized by an optical feedback loop. A single optical fiber directs the beams to the skin and collects the reflected light back to a photodetector, the signal of which is sampled and Fourier transformed to give a frequency power spectrum. Several models of light scattering by the skin are examined, and a single Lorentzian function is found to be the best fit for our experimental power spectra. Flow parameters have been thus measured for several in vitro and in vivo situations. In vitro calibration indicates that there is a constant ratio between the frequency responses at both wavelengths used. The decrease of this ratio encountered in in vivo measurements is attributed to different depths of investigated skin microcirculation according to the incoming wavelengths.

Double-wavelength laser

A new technique is reported which allows a laser to operate simultaneoulsy at two or more wavelengths from a high-gain grating- or prism-tuned laser. This is done by inserting a small-angle wedge in the laser to form two independent cavities. The relative intensities at the output wavelengths are governed by the wedge location. Tuning of the new wavelength is accomplished by rotating the wedge. The difference frequency between the two output wavelengths is not limited by the gain characteristics of the active medium since different active media can be used simultaneously. The wedge technique was used in a nitrogen-laser-pumped dye laser and the usefulness of such a laser in nonlinear opitcal experiments was shown.