Continuous Wave Mode Research Articles

Logic gates through three core and dual core nonlinear directional couplers operating in continuous wave mode

Logic gates through three core and dual core nonlinear directional couplers operating in continuous wave mode

Применение лазера с длиной волны 445 нм в хирургии гортани: экспериментальное исследование

Introduction. The problem of phonosurgery remains relevant today since the prevalence of benign and tumor-like laryngeal lesions is up to 55%–70% among diseases of the upper respiratory tract. Photoangiolytic lasers are actively used among laser systems in phonosurgery today. A new 445 nm surgical laser (TruBlue, A.R.C. Laser Company), having a high hemostatic and resection effects, was certified for the medical market in 2018. TruBlue laser operation is possible in an atmosphere of inert gas (helium) by connecting the optional Flow Control unit. To date, there are very few works in foreign and Russian literature devoted to the use of that laser device in ENT practice, particularly, in laryngology. Objective. To select the optimal 445 nm laser mode for use in phonosurgery based on an experimental study of biological material. Material and methods. An experimental study was conducted on a model of the larynx (chicken muscle tissue) using a 445 nm laser in contact constant and pulsed modes, including an atmosphere of an inert gas (helium). The zones of destruction, coagulation necrosis, and ischemia were measured by histological examination using a morphometry system. The total number of experiments was 142, the total number of micro-preparations studied was 284. Results. While working in continuous wave mode, we received an extensive zone of thermal exposure, which in clinical practice correlates with deep damage of the vocal fold and violation of its vibratory function. This confirms the axiom that the optimal mode for laryngeal surgery is a pulsed one. According to the evaluation results of the pulse mode at standard laser settings (without helium supply), the parameters with the smallest pause between pulses—that is, 8 W pulse 10–20 ms, 9–10 W pulse 10 ms with a pause of 150 ms—were the most optimal for practical activity in terms of combined resection and coagulation effect. These parameters are acceptable for use in phonosurgery since the maximum destruction zone does not exceed 600 nm. While working in an inert gas atmosphere, we recommend using a laser at a power of 6–8 W with a pulse duration of 10 ms and a pause of 100–130 ms; with an increase in the pulse, lengthen the pause 6–7 W 20 ms 120–130 ms, 8 W 20 ms with a pause of 130 ms. Conclusion. During the experiment, blue laser showed high resection and coagulation effects. According to the results of the study, the parameters of laser exposure were obtained, which are optimal for the surgical treatment of benign and tumor-like laryngeal lesions.

Low-level laser periodontal therapy in diabetic patients: a randomized controlled clinical trial - pilot study

Objectives We aimed to evaluate the effects of low-level laser therapy as an adjunct to non-surgical periodontal therapy in patients with periodontitis and compare the effect on periodontal healing in diabetes mellitus and non-diabetes mellitus patients. Methodology Ten patients with periodontitis stage II grade B were divided into two groups; Group 1 included 5 non-diabetes mellitus patients with periodontitis, and Group 2 included 5 type2 diabetes mellitus patients with periodontitis. A 13 mW low-level laser was used in a continuous wave and non-contact mode as an adjunct to scaling and root planning (SRP) in a split-mouth study design “OPTODAN” (Scientific Development and Production Center, Saratov, Russia). The clinical parameters; plaque and gingival index, probing depth, and relative clinical attachment level of the test and control sides of both groups were analyzed at baseline and 1-month post-therapy. Visual analogue scale was used to determine patient discomfort intraoperatively and after 1 week. Results Statistically, significant improvement was evident in the gingival index, probing depth, and relative clinical attachment level when comparing test and control sides in all patients 1-month post-therapy. There was improvement in gingival index amongst type 2 diabetes mellitus patients in the test group. However, non-diabetes mellitus patients demonstrated superior results especially in probing depth and relative clinical attachment level. Conclusion The use of low-level laser therapy as an adjunct in periodontal therapy showed overall improvement in gingival inflammation, probing depth, and clinical attachment level. In comparison to non-diabetes mellitus patients, type 2 diabetes mellitus patients demonstrated significant improvement in gingival inflammation with low-level laser therapy.

Electron-Optic System With High Compression of a Multiple Elliptic Electron Beam for a Miniaturized THz-Band Vacuum Electron Device

Electron-optic systems (EOSs) with high compression are required for THz-band vacuum-tube electron devices to reduce the cathode load, which is necessary to increase lifetime and enable operation in a continuous-wave (CW) mode. However, it is difficult to achieve high compression of multiple electron beams. In this article, we present the design and simulation of EOS with triple elliptic electron beam for a 0.2-THz traveling-wave tube. The triode electron gun with planar electrodes provides <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times 0.06$ </tex-math></inline-formula> -A electron beam with compression factor of 16. At the cathode, the current density is 26.31 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while in the beam tunnel it is higher than 400 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The magnetic focusing system with 1.34-T axial magnetic field consisting of Nd–Fe–B permanent magnets and pole pieces is also designed. The numerical simulation predicts stable beam transmission at 25-mm distance.

Parameter Design and Imaging Method of Spaceborne Azimuth Interrupted FMCW SAR

Spaceborne azimuth interrupted frequency modulation continuous wave (AI-FMCW) synthetic aperture radar (SAR), known as a novel system to observe the characteristics of ground objects, employs a single antenna to transmit and receive continuous waves, thus different from traditional frequency modulated continuous wave (FMCW) SAR that needs two antennas. However, due to the single antenna, there is a phenomenon that the transmitting of several continuous waves could be unavailable while replaced by receiving radar echoes. The process of switching the transmitter ON and OFF will leave gaps in the synthetic aperture. In this case, traditional imaging algorithms such as the wavenumber domain algorithm (WDA) cannot acquire clear focused images, resulting in the blurred ones corrupted by ghost targets. To solve the problem mentioned above, this letter presents an image restoration algorithm to improve the AI-FMCW SAR image performance. In this letter, there are two main contributions: 1) some key parameters of the AI-FMCW SAR system are designed and 2) a method based on Richardson–Lucy (RL) deconvolution algorithm is applied to AI-FMCW SAR imaging to suppress ghost targets. Finally, a case of the Ku-band AI-FMCW SAR system is given, and experiments via simulated AI-FMCW SAR data are conducted to validate the proposed method.

Impact of Adjunctive Laser Irradiation on the Bacterial Load of Dental Root Canals: A Randomized Controlled Clinical Trial.

Successful root canal treatment depends on the adequate elimination of pathogenic bacteria. This study evaluated the effectiveness of a novel 445-nm semiconductor laser in reducing bacteria after chemomechanical root canal treatment. Microbiological specimens from 57 patients were collected after emergency endodontic treatment, in the following sequence: 1, removal of the temporary filling material; 2, chemomechanical treatment; 3, rinsing with sodium hypochlorite (3%) along with one of three adjuvant protocols (n = 19 in each group). The adjuvant procedures were: (a) sodium hypochlorite rinsing alone (3%); (b) laser irradiation; (c) combined sodium hypochlorite rinsing and laser irradiation. The diode laser was set to 0.59 W in continuous-wave mode (CW) for 4 × 10 s. After the flooding of the root canal with saline, specimens were collected using paper points and analyzed microbiologically. Statistically significant reductions in the bacterial load were observed in all three groups (p < 0.05): 80.5% with sodium hypochlorite rinsing alone and 58.2% with laser therapy. Both results were lower than with the combination of sodium hypochlorite rinsing and 445-nm laser irradiation, at 92.7% (p < 0.05). Additional disinfection of the root canal can thus be achieved with 445-nm laser irradiation after conventional chemical disinfection with sodium hypochlorite solution.

Fault detection performance of a multi-mode transmission reflection analysis for a few-mode fiber link.

We propose a novel monitoring technique based on multi-mode transmission reflection analysis for a long-reach few-mode fiber (FMF) based mode division multiplexing system. By launching unmodulated continuous-wave optical light modes into the corresponding spatial modes of the FMF, the transmitted and reflected or backscattered optical powers can be measured and quantitatively analyzed to accurately characterize and locate the fault. The influences of the capture fraction, attenuation coefficient, and Rayleigh backscattering coefficient are discussed, and simulation results show that the proposed method can realize the fault location of the FMF link. Moreover, considering the influence of mode crosstalk on localization accuracy, it is clear that using the monitoring combination modes LP01 and LP21 gives a high precision of 3.58 m.

Developing of Algorithms Monitoring Heartbeat and Respiration Rate of a Seated Person with an FMCW Radar

Abstract. With a radar working in the 24 GHz ISM-band in a frequency modulated continuous wave mode the major vital signs heartbeat and respiration rate are monitored. The observation is hereby contactless with the patient sitting straight up in a distance of 1–2 m to the radar. Radar and sampling platform are components developed internally in the university institution. The communication with the radar is handled with MATLAB via TCP/IP. The signal processing and real-time visualization is developed in MATLAB, too. Cornerstone of this publication are the wavelet packet transformation and a spectral frequency estimation for vital sign calculation. The wavelet transformation allows a fine tuning of frequency subspaces, separating the heartbeat signal from the respiration and more important from noise and other movement. Heartbeat and respiration are monitored independently and compared to parallel recorded ECG-data.

Low-cost camera-based pulsed and modulated continuous wave laser detection for laser-based optical communications

A novel, low-cost, camera-based method of detecting a single nanosecond (ns) laser pulse and kHz modulated continuous wave and pulsed lasers has been developed. The detector uses a simple optical modification to a standard rolling shutter color camera combined with image processing techniques to distinguish lasers from other illumination sources and extract a laser’s wavelength and pulse repetition frequency. In addition, the detector is also capable of detecting a single ns laser pulse at any given time. Such a detector has applications in free-space optical communications (FSO comms) as a low-cost broadband method of extracting information from multiple sources and as a detector of laser range finders. A low-cost prototype (≈£600) has been developed using entirely off-the-shelf components and assessed in laboratory and field trial conditions, with the ability to measure laser wavelengths to ±5 nm and pulse repetition frequencies to within ±5 % at a distance of 660 m. In the laboratory, the prototype was also able to detect each of the 1000 pulses generated by a 10 Hz 10 ns 532-nm pulsed laser, as well as 100 pulses sent at random intervals, highlighting its capability to detect a ns pulse at any given time. This novel technology offers a low-cost method of detecting lasers and extracting their pulse repetition frequencies, with a wide field of view and high spatial resolution. Ultimately, this technology has applications in FSO comms for between vehicles or platforms of interest, with a capability of communicating with multiple targets simultaneously.

Applications of radar measurement technology using 24 GHz, 61 GHz, 80 GHz and 122 GHz FMCW radar sensors

Abstract This paper presents a review of radar applications in high-accuracy distance measurement of a target. The radars included in this review are frequency modulated continuous wave (FMCW) radar sensors operating in four different millimeter-wave frequency bands, namely 24 GHz, 61 GHz, 80 GHz and 122 GHz. The radar sensors are used to measure the distance of standard and complex targets in a short range of a few meters, thus indicating that the choice of target and the medium used for radar signal propagation also play a key role in determining the distance measurement accuracy of an FMCW radar. The standard target is a trihedral corner reflector in a laboratory-based free space measurement setup and the complex targets include a piston in an oil-filled hydraulic cylinder and a planar positioning stage used in micromachining. In each of these measurement scenarios, a distance measurement accuracy in micrometer range is achieved due to the use of a sophisticated signal processing algorithm that is based on a combined frequency and phase estimation method. The paper is concluded with a technical comparison of the accuracy achieved by the FMCW radars reviewed in this article with other related works.

Medium-velocity superconducting cavity for high accelerating gradient continuous-wave hadron linear accelerators

We present the first rf studies of the medium-$\ensuremath{\beta}$ superconducting radio frequency (SRF) elliptical cavities designed for Michigan State University's Facility for Rare Isotope Beams (FRIB) energy upgrade linac. The proposed energy upgrade for this continuous-wave (CW) superconducting linac will double the final beam energy from 200 to $400\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$ for the heaviest uranium ions within the 80 m of space available in the FRIB tunnel. Two prototype ${\ensuremath{\beta}}_{\mathrm{opt}}=0.65\text{ }644\text{ }\text{ }\mathrm{MHz}$ five-cell elliptical SRF cavities were fabricated and tested to validate the novel cavity design with three conventional rf recipes: (1) Electropolishing (EP-only), (2) $\mathrm{EP}+48\text{ }\text{ }\mathrm{h}$ $120\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ bake ($\mathrm{EP}+\text{baking}$), and (3) Buffered chemical $\text{Polishing}+48\text{ }\text{ }\mathrm{h}$ $120\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ bake ($\mathrm{BCP}+\text{baking}$). The EP-only recipe achieved a 2 K quality factor (${Q}_{0}$) of $2.3\ifmmode\times\else\texttimes\fi{}{10}^{10}$ at the FRIB energy upgrade design accelerating gradient (${E}_{\text{acc}}$) of $17.5\text{ }\text{ }\mathrm{MV}/\mathrm{m}$, and ${Q}_{0}$ of $1.2\ifmmode\times\else\texttimes\fi{}{10}^{10}$ at a maximum gradient of $26\text{ }\text{ }\mathrm{MV}/\mathrm{m}$, where the gradient was ultimately limited by the available rf amplifier power available for this test. These results validate the potential of the novel 644 MHz medium-$\ensuremath{\beta}$ cavity design and motivate its use in future high-${\mathrm{Q}}_{0}$ development work. The multipacting band, which exists at ${E}_{\mathrm{acc}}\ensuremath{\approx}10\text{ }\text{ }\mathrm{MV}/\mathrm{m}$, was completely conditioned in the continuous-wave mode. We also observed that combining the 48 h $120\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ baking treatment with EP did not improve the EP-only cavity performance at 2 K due to increased residual resistance (${R}_{0}$) and increased medium-field Q-slope. $\mathrm{BCP}+\text{baking}$ was also found to produce lower ${\mathrm{Q}}_{0}$ in this cavity due to increased medium-field Q-slope. The mechanical modes of this cavity were measured at room temperature, verifying that the quality factor of the dominant ``accordion'' mechanical mode these medium-$\ensuremath{\beta}$ cavities are particularly vulnerable to is close to that of the 1.3 GHz TESLA cavities. Thus, this mode arising from the novel geometry of these cavities is shown to not be of excessive concern for resonance control.

808-nm Photobiomodulation Affects the Viability of a Head and Neck Squamous Carcinoma Cellular Model, Acting on Energy Metabolism and Oxidative Stress Production

Photobiomodulation (PBM) is a form of low-dose light therapy that acts through energy delivery from non-ionizing sources. During the recent two decades, there has been tremendous progress with PBM acceptance in medicine. However, PBM effects on potential stimulation of existing malignant or pre-malignant cells remain unknown. Thus, the primary endpoint was to assess the safety of PBM treatment parameters on head and neck squamous cell carcinoma (HNSCC) proliferation or survival. The secondary endpoint was to assess any putative anti-cancer effects of PBM treatments. Cell viability, energy metabolism, oxidative stress, and pro- and anti-apoptotic markers expression were investigated on a Human Head and Neck Squamous Cell Carcinoma cellular model (OHSU-974 FAcorr cell line). PBM therapy was administered through the 810 nm diode laser (GaAlAs) device (Garda Laser, 7024 Negrar, Verona, Italy) at the powers of 0, 0.25, 0.50, 0.75, 1.00, or 1.25 W in continuous wave (CW) mode for an exposure time of 60 s with a spot-size of 1 cm2 and with a distance of 1.86 cm from the cells. Results showed that 810-nm PBM affected oxidative phosphorylation in OHSU-971 FAcorr, causing a metabolic switch to anaerobic glycolysis. In addition, PBM reduced the catalase activity, determining an unbalance between oxidative stress production and the antioxidant defenses, which could stimulate the pro-apoptotic cellular pathways. Our data, at the parameters investigated, suggest the safeness of PBM as a supportive cancer therapy. Pre-clinical and clinical studies are necessary to confirm the in vitro evidence.

Development of plasma beam irradiation facility using applied-field MPD thruster to study plasma-surface interactions

A plasma beam irradiation facility was developed based on the applied-field magnetoplasmadynamic (AF-MPD) thruster concept for studying plasma-surface interactions. The AF-MPD thruster was chosen because it can produce a plasma beam with high plasma density in continuous-wave mode. Two types of AF-MPD thruster were developed and used in this study: a type I source with a wide thruster channel was used for a heat flux test with Ar or Xe gas, while a type II source with a narrow thruster channel was used for an ion flux test with H2 or He gas. The plasma initially showed the characteristics of abnormal glow discharges and then a transition to arc occurred when the plasma current exceeded a threshold value. It was found that a cathode made of thoriated tungsten significantly lowered the threshold current for the transition from abnormal glow to arc. The maximum heat flux provided by our facility was measured to be 7 MW m−2 using a custom-made heat flux sensor, while the maximum hydrogen ion flux was measured to be 1 × 1023 m−2 s−1 using a Langmuir probe. The electron temperature ranged between (4–5) eV, while the electron density at the plasma plume (downstream) ranged between (1–4) × 1018 m−3.

Assessment of steel shields for protection against laser radiation

High-power laser processing shows increasing importance in the manufacturing industry. Solid-state lasers provide optical powers of several kilowatts in continuous-wave mode with power densities of more than 1 MW/mm2, thus helping to achieve economically relevant processing speeds. However, to minimize health risks due to intense laser radiation, sophisticated safety concepts are required. An essential part of these concepts is the laser-process housing, which typically consists of metallic walls as passive shielding against laser radiation. The standard EN 60825-4 defines requirements and testing conditions for these shielding materials. Here, it is considered that the material durability depends not only on the laser irradiance on the material surface but also on the laser-spot size, which is attributed to hindered heat conduction at the spot edge due to heat accumulation occurring at larger spot sizes. However, this behavior has not been fully understood. In this work, a simplified finite-element modeling approach based on the heat equation is used to simulate the dependence of the material durability on the laser-spot size for 2 mm thick structural steel, a typical shielding material in industry. The calculated times to reach the material-melting temperature are compared with the measured material lifetimes upon laser irradiation. It is shown that the presented finite-element modeling can reproduce the general size dependence of the material durability. Thus, this analysis to calculate the times up to the material-melting start can be used to derive lower limits of the material lifetimes under defined irradiation conditions, suitable for designing the shielding sufficiently.

High power λ ~ 8.5 μm quantum cascade laser grown by MOCVD operating continuous-wave up to 408 K

Robust quantum cascade laser (QCL) enduring high temperature continuous-wave (CW) operation is of critical importance for some applications. We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition (MOCVD). High interface quality structures designed for light emission at 8.5 μm are achieved by optimizing and precise controlling of growth conditions. A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10 μm-wide coated laser. Corresponding maximum wall-plug efficiency and threshold current density were 7.1% and 1.18 kA/cm2, respectively. The device can operate in CW mode up to 408 K with an output power of 160 mW.

P-doped 1300 nm InAs/GaAs quantum dot lasers directly grown on an SOI substrate.

The realization of monolithic integration of a stable III-V laser on a standard silicon-on-insulator (SOI) substrate has been regarded as a challenging technology for silicon-based photonic integration circuits (PICs). Here, we successfully demonstrated the electrically pumped P-doped 1300 nm InAs/GaAs quantum dot (QD) laser epitaxially grown on {111}-faceted SOI hollow substrates. These III-V QD lasers, which are epitaxially grown on an SOI substrate, generally exhibit strong thermal accumulation due to the oxide layer underneath. By applying a double-side heat dissipation design, the maximum operation temperature of the SOI-based InAs/GaAs QD laser under a continuous-wave (CW) operation mode is ramped up to 35°C from 20°C. Moreover, the thermal profile simulation of three different structures has also been carried out to show the effectiveness of the top heat sink design in order to improve laser performance. An integrated thermal shunt design is proposed to improve heat dissipation without using the external top heat sink. The successful realization of room-temperature SOI-based InAs/GaAs QD lasers pave a viable way for integrating light sources in PICs.

Effect of light-emitting diode phototherapy on pain and trismus following surgical extraction of impacted mandibular third molars

Purpose: This study aimed to assess the effect of light-emitting diode (LED) phototherapy on pain and trismus following surgical extraction of impacted mandibular third molars. Materials and Methods: This double-blind randomized controlled clinical trial evaluated 50 patients between 20 to 35 years requiring extraction of their impacted mandibular third molars. The patients were randomized into two groups of LED phototherapy and control by flipping a coin. Patients in the LED group underwent LED phototherapy immediately after surgery with red light at 618nm wavelength, 20 mW/cm2 power density and 4 J/cm2 energy density in continuous-wave mode (irradiated area: 3.15cm×1.5cm=4.725cm2). The LED device was used in off mode in the control group (as placebo). The level of postoperative pain was measured by the numerical rating scale, and trismus of patients was evaluated by measuring the maximum mouth opening (MMO). The two groups were compared by the Mann-Whitney and NPar tests. Results: The mean difference in MMO postoperatively, compared with baseline, was lower in the LED group than the placebo group but not significantly (P=0.465). The two groups were not significantly different regarding the level of pain. Conclusion: LED phototherapy with the parameters applied in this study failed to significantly decrease the level of pain and trismus following surgical extraction of impacted mandibular third molars.

Single photon Lidar gas imagers for practical and widespread continuous methane monitoring

The accurate and comprehensive identification and quantification of greenhouse gas (GHG) emissions is an essential part of the management and mitigation of climate change. We are developing a novel remote gas imaging sensor for the detection, visualisation, and quantification of methane emissions. The sensor uses a new technique we call Tunable Diode Lidar (TDLidar) which combines aspects of Tunable Diode Laser Absorption Spectroscopy (TDLAS) with Differential Absorption Lidar (DIAL) and Time Correlated Single Photon Counting (TCSPC) to enable remote spectroscopy and ranging with low power semiconductor diode lasers. Our first TDLidar methane sensors use diode lasers with wavelengths around the CH4 absorption line at 1.6509 μm and Peltier-cooled Single Photon Avalanche Diode (SPAD) detectors in a Random Modulation Continuous Wave (RM-CW) Lidar system. Here we characterise our TDLidar methane sensor performance with calibrated gas cells and controlled gas release trials and we demonstrate quantification of leak rates as low as 0.012 g/s and detection at distances over 90 m. The accuracy, speed, and practicality of the sensor, combined with an expectation of low-cost in volume, offers the potential that these sensors can be effectively applied for widespread continuous and autonomous monitoring of industrial methane emissions.

The Evaluation of the Effectiveness of the Optimized Technique of Transcleral Diodlaser Cyclophotocoagulation in Patients with Unstable Glaucoma

Objectives: To evaluate the effectiveness of the optimized technique of transcleral diode laser cyclophotocoagulation (DCPC) in patients with unstable glaucoma.Methods. The retrospective analysis of outpatient records of patients diagnosed with open-angle compensated glaucoma, who underwent transcleral diodlaser DCPC in continuous-wave mode, has been performed. Totally, 44 outpatient records (44 eyes) have been analyzed.Results. The course of the postoperative period, patients’ complaints, and the ophthalmological status have been evaluated. The level of intraocular pressure (IOP) was determined on the day after the procedure, a week, 1, 3, 6 and 12 months after the operation. 12 months after the operation, the level of IOP decreased by 42.9 %. The number of antihypertensive drugs used by the end of the follow-up period decreased by 66.6 %: from 2.75 ± 0.4 to 1.0 ± 0.7 drugs (p = 0.001). The frequency of side effects was low and comprised 11.3 %. In 40 % of patients, manifestations of toxic-allergic reactions of the ocular surface to antihypertensive drugs decreased due to the possibility to reduce the frequency of instillations. The MCVA indicators remained stable throughout the entire follow-up period.Conclusion. Thus, the results of the conducted clinical study indicate that transcleral DCPC is an effective and safe technique with a high predicted result, since it compensates for the level of IOP, which allows to stabilize the progression of the glaucoma process. The method of trascleral DCPC provides a reduction and (or) correction of the hypotensive regime by reducing the number of antihypertensive drugs used. In patients with a toxic-allergic reaction from the ocular surface developed due to a prolonged use of antihypertensive drugs, it allows to reduce the symptoms and clinical manifestations by canceling and (or) reducing the number of antihypertensive drugs used, indirectly significantly improving the quality of life.

Continuous wave vertical emission from terahertz microcavity lasers with a dual injection scheme.

Quantum cascade lasers (QCLs) represent a most promising compact source at terahertz (THz) frequencies, but efficiency of their continuous wave (CW) operation still needs to be improved to achieve large-scale exploitation. Here, we demonstrate highly efficient operation of a subwavelength microcavity laser consisting of two evanescently coupled whispering gallery microdisk resonators. Exploiting a dual injection scheme for the laser cavity, single mode CW vertical emission at 3.3 THz is obtained at 10 K with 6.4 mA threshold current and 145 mW/A slope efficiency up to 320 μW emitted power measured in quasi-CW mode. The tuning of the laser emission directionality is also obtained by independently varying the pumping strength between the microdisks. By connecting the resonators through a suspended gold bridge, the laser out-coupling efficiency in the vertical direction is strongly enhanced. Owing to the high brightness, low-power consumption and CW operation, the proposed microcavity laser design could allow the realization of high-performance CW THz QCLs ready for massive parallelization.