Standard Laser Research Articles

The Efficacy of Tumor Characterization for Colorectal Lesions with Blue Light Imaging of a Compact Light-Emitting Diode Endoscopic System Compared to a Laser Endoscopic System: A Pilot Study.

Background: A compact and cost-effective light source-processor combined 3-color light-emitting diode (LED) endoscopic system (ELUXEO-Lite: EP-6000, Fujifilm Co., Tokyo) with a magnified colonoscope (EC-6600ZP, Fujifilm Co.) has been released. Aims: In this study, we analyzed the efficacy of this system for colorectal tumor characterization with magnified blue light imaging (BLI-LED) and image's subjective and objective evaluations, compared to a magnified blue laser imaging (BLI-LASER) using a standard LASER endoscopic system. Methods: We retrospectively reviewed 37 lesions observed with both BLI-LED and BLI-LASER systems from 2019 using the Japanese narrow band imaging classification. Two representative magnified images, one BLI-LED and one BLI-LASER, of the same area of a lesion were evaluated for diagnostic accuracy and visualization quality by three experts and three non-experts. Their color difference values (CDVs) and brightness values (BVs) were also calculated as objective indicators. Results: Among 37 lesions, mean tumor size was 18.9 ± 13.1 mm, and 21 lesions were nonpolypoid. Histopathology revealed 14 sessile serrated lesions, 7 adenomas, 12 high-grade dysplasias and T1a cancers, and 4 T1b cancers. The diagnostic accuracy rates of BLI-LED/BLI-LASER of experts and non-experts were 90.1% and 87.4% (p = 0.52) and 89.2% and 89.2% (p = 0.99). The percentages of instances where BLI-LED images were better, the two imaging types were equivalent, or BLI-LASER images were better were 16%/83%/1% for experts and 19%/58%/23% for non-experts (p < 0.001). CDVs and BVs between BLI-LED and BLI-LASER were not significantly different (CDVs: p = 0.653, BVs: p = 0.518). Conclusions: BLI-LED using the compact system was noninferior to BLI-LASER for colorectal tumor characterization and image quality.

Development of magnetic nanoparticle assisted aptamer-quantum dot based biosensor for the detection of Escherichia coli in water samples

The contamination of food and potable water with microorganisms may cause food-borne and water-borne diseases. The common contaminants include Escherichia coli (E. coli), Salmonella sp. etc. The conventional methods for monitoring the water quality for the presence of bacterial contaminants are time-consuming, expensive, and not suitable for rapid on-spot detection in field conditions. In the current study, super paramagnetic iron oxide nanoparticles (SPIONs) were synthesized and conjugated with E. coli specific Aptamer I to detect E. coli cells qualitatively as well as quantitatively. The sludge consisting of E. coli- SPION complex was separated via magnetic separation. The presence of E. coli cells was confirmed with the help of standard techniques and confocal laser scanning microscopy (CLSM) employing Aptamer II conjugated CdTe-MPA quantum dots (QDs). Finally, an ATmega 328P prototype biosensor based on Aptamer II conjugated CdTe MPA QDs exhibited quantitative and qualitative abilities to detect E.coli. This prototype biosensor can even detect low bacterial counts (up to 1 × 102 cfu) with the help of a photodiode and plano-convex lens. Further, the prototype biosensor made up of ultraviolet light-emitting diode (UV LED), liquid crystal display (LCD) and ATmega328Pmicrocontroller offers on-spot detection of E.coli in water samples with high resolution and sensitivity. Similarly, this in-house developed prototype biosensor can also be utilized to detect bacterial contamination in food samples.

Thulium Fibre Laser versus Holmium:YAG for Ureteroscopic Lithotripsy: Outcomes from a Prospective Randomised Clinical Trial

BackgroundHolmium:yttrium-aluminium-garnet (Ho:YAG) laser is the gold standard for ureterorenoscopic (URS) lithotripsy. Thulium fibre laser (TFL) has recently been introduced as a new technology and may challenge Ho:YAG as the preferred laser owing to favourable properties as demonstrated in preclinical studies. ObjectiveTo evaluate and compare outcomes after URS lithotripsy with Ho:YAG and TFL. Design, setting, and participantsIn a prospective randomised trial, patients aged ≥18 yr with ureteral and/or renal stones (≥5 mm) scheduled to undergo day-case URS lithotripsy were invited to participate. In total, 120 consecutively admitted patients with signed consent were included for randomisation. InterventionURS lithotripsy with Ho:YAG or TFL. Outcome measurements and statistical analysisThe primary outcome was the stone-free rate (SFR) assessed on noncontrast computed tomography at 3-mo follow-up. Secondary outcomes were the operative time and complications. Outcomes were compared between the groups using the t test and χ2 test. Results and limitationsAfter a single session, the SFR was 67% in the Ho:YAG group and 92% in the TFL group, p = 0.001. For ureteral stones, the SFR was 100% in both groups, and for renal stones; 49% (Ho:YAG) and 86% (TFL), p = 0.001. Operative time was shorter using TFL (49 min) compared to Ho:YAG (57 min), p = 0.008. Bleeding that impaired the endoscopic view was the most frequent intraoperative adverse event and occurred in 13 patients (22%) in the Ho:YAG group and three (5%) in the TFL group, p = 0.014. ConclusionsIn this study, significantly more patients with renal stones achieved stone-free status and fewer experienced intraoperative complications using TFL compared to Ho:YAG. TFL is the emerging laser of choice for stone lithotripsy. Patient summaryWe compared outcomes after ureterorenoscopic treatment of kidney and ureteral stones using two different lasers. Our results show that the new thulium fibre laser technology is superior to the current standard laser (holmium:YAG) in clearing kidney stones and reducing operative complications.

Development of 2.45 GHz Semiconductor Microwave System for Combustion Ignition Enhancement and Failure Analysis.

We developed a semiconductor microwave system to improve the ignition process in a combustion system. Under atmospheric pressure conditions, large plasma was successfully ignited by a 2.45 GHz microwave, and it is characterized in comparison with standard spark plug ignition and laser ignition. The size of the microwave power source was also effectively reduced with the minimal size (100 × 60 mm2) that could fit in the palm of a hand. We then prototyped a microwave plug with a diameter of 4 mm, which is smaller than the standard spark plugs for passenger cars. The design and electric field strength are discussed in detail. Combustion experiments were conducted using a motorcycle engine and an actual light vehicle, and significant fuel efficiency improvement was experimentally obtained. We investigated the wear of the plug caused by continuous operation, and efficiently improved the endurance by swinging the resonance frequency between 2.4 and 2.5 GHz. In a passenger car engine experiment using a flat panel igniter, significant fuel efficiency improvement was confirmed. Further failure analysis revealed that the ceramic was severely damaged by a large current surge.

Holmium: yttrium-aluminum-garnet laser with Moses: does it make a difference?

Moses effect is an inherent physical principle of Ho:YAG laser functioning. Moses Technology is a pulse modulation modality of Ho:YAG laser, which became commercially available for the treatment of two urological conditions: urinary stones and benign prostatic obstruction. The purpose of this narrative review is to distinguish between Moses effect and Moses Technology, as well as to summarize the latest evidence on Moses Technology and its main application in the urological field. During laboratory lithotripsy, Moses Technology seems to reduce stone retropulsion and determine higher ablation volume compared with regular lithotripsy. However, this technology presents similar characteristics to long pulse Ho:YAG laser, and several studies showed no significant difference between Moses Technology and standard lasers. When used in prostate enucleation, Moses Technology promises to reduce operating time by increasing the efficiency of prostate resection and improve the hemostasis. Moreover, some studies state that it is possible to reduce the HoLEP morbidity. Despite this, the clinical impact of the time reduction remains uncertain and different studies either present relevant limitations or are burdened by significant bias. Although Moses effect has been extensively described and characterized, and several studies have been published on the usage of Moses Technology for both laser lithotripsy and laser enucleation of the prostate with Holmium YAG, solid clinical evidence on the real improvement of surgical outcomes is still missing.

Myopic outcome after intraocular lens implantation in a patient who previously had small-incision lenticule extraction

Introduction: This is a report of cataract surgery in a post–small-incision lenticule extraction (SMILE) patient with low myopia. Patient and clinical findings: A 49-year-old man underwent bilateral SMILE 18 months previously, and the visual acuity of both eyes recovered to 20/20. The patient noticed a gradual reduction in visual acuity in his left eye and blurring for 3 months. The corrected distance visual acuity (CDVA) was 20/67 in his left eye. Diagnosis, intervention, and outcomes: The slitlamp examination revealed an anterior subcapsular cataract. The intraocular lens (IOL) power was calculated by using a multiformula averaging method. A standard femtosecond laser–assisted phacoemulsification cataract surgery was performed and a trifocal IOL implanted. 2 months after IOL implantation, the uncorrected distance visual acuity of the left eye was 20/33, the autorefraction values were −1.37 −0.25 × 146, and the CDVA was 20/20. Conclusions: This case report showed that current postrefractive IOL power calculation formulas or methods may lead to myopic outcomes in patients who previously received SMILE. A standard IOL calculation may be more suitable for such patients. Additional case studies are needed to accurately calculate IOL power after SMILE similar to laser in situ keratomileusis.

Raman spectra of twisted bilayer graphene close to the magic angle

In this work, we study the Raman spectra of twisted bilayer graphene samples as a function of their twist-angles (θ), ranging from 0.03° to 3.40°, where local θ are determined by analysis of their associated moiré superlattices, as imaged by scanning microwave impedance microscopy. Three standard excitation laser lines are used (457, 532, and 633 nm wavelengths), and the main Raman active graphene bands (G and 2D) are considered. Our results reveal that electron–phonon interaction influences the G band’s linewidth close to the magic angle regardless of laser excitation wavelength. Also, the 2D band lineshape in the θ < 1° regime is dictated by crystal lattice and depends on both the Bernal (AB and BA) stacking bilayer graphene and strain soliton regions (SP) (Gadelha et al 2021 Nature 590 405–9). We propose a geometrical model to explain the 2D lineshape variations, and from it, we estimate the SP width when moving towards the magic angle.

Approach based on χ2 to phasing segmented-mirror telescopes using multiple wavelengths: data reduction, wavelength selection, capture range.

The design of extremely large segmented-mirror telescopes (ELTs) calls for their segments to be phased, and a number of different interferometric techniques have been proposed in the literature for this purpose. To achieve the required large capture ranges for ELTs (typically a few microns), most of these techniques use measurements at multiple wavelengths, similar to what is done in standard distance-measuring laser interferometry. In this paper, we present a χ2-based framework not tied to a specific phasing technique to obtain intersegment edge heights from multiwavelength data. We show how this scheme can be used to select an optimal set of wavelengths that maximizes the capture range while achieving the very low error rates required for ELT phasing. We take into account the wavelength uncertainty associated with the finite-width interference filters used in on-sky phasing. Finally, we present data from the Keck 2 telescope that illustrate the method for three-wavelength phasing.

Operating room noise hazards during laser lithotripsy: a comparison between the thulium fiber and holmium laser platforms.

To evaluate and assess the impact of noise hazard during laser lithotripsy using the gold standard holmium:YAG laser and the novel thulium fiber laser (TFL). Intraoperative noise measurements were obtained during ureteroscopy and laser lithotripsy from cases using both TFL and holmium laser. Readings were obtained from three key times: prior to laser activation, with the laser on but idle, and during laser activation. Questionnaires were circulated postoperatively to operating room staff regarding the effort required to perform tasks, concentrate, and communicate during the surgery. Noise levels were compared from 16 TFL and 15 holmium laser lithotripsy cases from 11/2020 to 5/2021. Significantly higher noise levels were recorded during holmium lithotripsy, with a mean of 3.1dB and 4.3dB higher noise with the device idle and device active, respectively. When compared to baseline noise with the device off, the holmium laser had a significant rise in recorded dB where the TFL had no statistically significant rise in noise over baseline once the laser was turned on. Operating room team members rated the noise level lower and the level of effort required for concentration, communication, and task completion lower with the TFL. The TFL produces 3.1 to 4.3dB less noise than the standard holmium laser, which, because of the logarithmic nature of the dB scale, translates into less than one half the overall noise energy. There was also less effort required by operating room staff to complete critical tasks during the quieter TFL cases.

“En-Bloc” Enucleation With Early Apical Release Compared to Standard Holmium Laser Enucleation of the Prostate: A Retrospective Pilot Study During the Initial Learning Curve of a Single Surgeon

To compare operative efficiency of Holmium laser enucleation of the prostate (HoLEP) using both the standard multi-incisional approach and en-bloc enucleation with early apical release during the initial learning curve. We retrospectively reviewed the initial 95 consecutive men who underwent HoLEP between April 2019 and September 2020 by a single surgeon. We compared patient demographics, and pre-, intra-, and post-operative metrics between both groups. Differences between groups were evaluated with Mann-Whitney U and Kruskal-Wallis tests. Forty-nine patients underwent the standard HoLEP approach, and 46 patients underwent the en-bloc approach. Compared to a standard HoLEP, the en-bloc approach was associated with decreased operative time (131.11 minutes vs 153.59 minutes, P=.007) with similar weights of tissue removed. Operative efficiency, as measured by grams of prostate tissue removed per minute, was greater for the en-bloc approach (0.49 g/min vs 0.36 g/min, P=.005). There was no difference in length of stay (0.91 days vs 0.96 days, P=.383), laser efficiency (4.41 kJ/g vs 4.83 kJ/g, P=.200), or number of post-operative complications (10 vs 6, P=.236) between the groups. Utilization of the en-bloc technique during the initial learning curve allows for a faster, more efficient operation without any difference in functional outcomes or major complications compared to a standard HoLEP.

Measuring the Lateral Diffusion of Plasma Membrane Receptors Using Raster Image Correlation Spectroscopy.

Raster image correlation spectroscopy (RICS) enables detecting and quantifying diffusion in live cells using standard commercial laser scanning confocal microscopes. Here, we describe a protocol based on RICS for measuring the lateral diffusion of two immunoreceptors within the plasma membrane of the macrophage cell line RAW 264.7. The sample images and measurements presented in this chapter were obtained from RICS analysis of Toll-like receptor 2 (TLR2) and cluster of differentiation 14 (CD14), which are transmembrane and membrane-anchored receptors, respectively. A step-by-step guideline is provided to acquire raster-scanned images and to extract the diffusion coefficients using RICS analysis.

Does Moses technology improve the efficiency and outcomes of standard holmium laser lithotripsy? A systematic review and meta-analysis.

Retrograde ureteroscopy with holmium laser lithotripsy (HLL) is a standard treatment for urolithiasis. Moses technology has been shown to improve fragmentation efficiency in vitro; however, it is still unclear how it performs clinically compared to standard HLL. We performed a systematic review and meta-analysis evaluating the differences in efficiency and outcomes between Moses mode and standard HLL. We searched the MEDLINE, EMBASE, and CENTRAL databases for randomized clinical trials and cohort studies comparing Moses mode and standard HLL in adults with urolithiasis. Outcomes of interest included operative (operation, fragmentation, and lasing times; total energy used; and ablation speed) and perioperative parameters (stone-free rate and overall complication rate). The search identified six studies eligible for analysis. Compared to standard HLL, Moses was associated with significantly shorter average lasing time (mean difference [MD] -0.95, 95% confidence interval [CI] -1.22 to -0.69 minutes), faster stone ablation speed (MD 30.45, 95% CI 11.56-49.33 mm3/min), and higher energy used (MD 1.04, 95% CI 0.33-1.76 kJ). Moses and standard HLL were not significantly different in terms of operation (MD -9.89, 95% CI -25.14 to 5.37 minutes) and fragmentation times (MD -1.71, 95% CI -11.81 to 8.38 minutes), as well as stone-free (odds ratio [OR] 1.04, 95% CI 0.73-1.49) and overall complication rates (OR 0.68, 95% CI 0.39-1.17). While perioperative outcomes were equivalent between Moses and standard HLL, Moses was associated with faster lasing time and stone ablation speeds at the expense of higher energy usage.

Laser micromachining of diamond: A viable photonic and optofluidic platform

We describe how the ultrafast laser micromachining technique applied with different writing methods can be used for the creation of various building blocks essential for the realization of a photonic and optofluidic diamond platform. Waveguides, NV centers, conductive wires, microchannels and microholes can be obtained thanks to laser microfabrication with suitable pulse parameters, making use not only of standard Gaussian laser beams but also of non-diffracting Bessel beams, the latter especially in all those cases where single pass high aspect-ratio microstructures or ablated areas are needed.

Triple Wavelength and 810 nm Diode Lasers for Hair Removal: A Clinical and &amp;lt;i&amp;gt;in Silico&amp;lt;/i&amp;gt; Comparative Study on Indian Skin

In laser hair removal treatments on dark skin, the high concentration of melanin in the skin competes with the melanin in the hair. During standard laser procedures, with wavelengths of 755 nm or 810 nm, a high level of laser light absorption by melanin in the skin is observed. Therefore, to avoid side effects, lower fluence values are used, which further reduces hair-removal efficacy. To improve results, 810 nm diode lasers operating in dynamic mode, with high frequency and multiple passes, are typically used. The aim of this study is to compare the efficacy and safety of triple-wavelength diode lasers (810 nm, 940 nm, 1060 nm) with that of 810 nm diode lasers on Indian patients. A side-by-side comparison was performed using a triple-wavelength diode laser in stamping mode on one side, and an 810 nm diode laser in dynamic mode on the other. Three subjects with skin type IV on the Fitzpatrick scale participated in the study. Efficacy was assessed through hair counting using clinical photographs, taken before and after the treatments, and the Global Aesthetic Improvement Scale (GAIS). Additionally, comparisons related to epidermal heating and thermal damage to the hair follicle were conducted through mathematical 3D simulations using COMSOL Multiphysics® software. Side effects were also evaluated. A superior end point was observed with triple wavelength compared to the 810 nm diode laser. Hair counting showed a 27% greater hair reduction with triple wavelength. No adverse effects were observed. Thermal simulations revealed 29% higher thermal damage with the triple-wavelength laser compared to the 810 nm diode laser. To conclude, on darker skin types, the triple-wavelength diode laser has been shown to be more effective at removing hair, compared to the 810 nm diode laser, while also being a safe procedure.

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.

Adaptable Fiber Laser Control Unit

Today fiber laser is widely used due to their performances and flexibility. They replace old types of lasers in the industrial machines. To develop a family of laser machines it is the need of having standard laser source that could efficiently be used and replaced in the equipment, independently of the laser source or types of lasers. This paper presents the concept and development of a new fiber laser control unit developed to be used for CW, QCW or pulsed regime. Control unit could be used in multiple laser source and satisfy complex requirements. The control unit of the fiber laser source is able to be used in a different type of fiber laser like: Yb doped fiber, Erbium fiber, thulium fiber. Control unit is designed to be used direct or with minimum modifications in different laser processing applications like: marking, engraving, cutting, drilling, welding, etc. Main parameters of control unit are: 3 working regime, frequency - 1 KHz (QCW), frequency in pulsed regime : 15KHZ - 500 KHz, control seed laser, control pre amplifier and amplifier. Control unit allows commands for machine control: start/stop, interlock, system ready/ fault.

Pregnancy outcomes following early fetoscopic laser photocoagulation for twin-to-twin transfusion syndrome at 16 weeks’ gestation

To evaluate perinatal outcomes following fetoscopic laser placental photocoagulation (FLPC) performed for twin-to-twin transfusion syndrome (TTTS) at 16 weeks’ gestation (16.0 – 16.9 weeks), as compared to FLPC performed at 17 weeks’ gestation and beyond. This retrospective review included monochorionic twins complicated by TTTS necessitating FLPC at a single tertiary center from 2012 to 2021, with cohorts defined as cases undergoing FLPC at 16.0 to 16.9 weeks (early laser group) and cases with FLPC at 17 weeks or greater (standard laser group). Primary outcomes included rates of immediate chorioamniotic membrane separation (CAS), preterm premature rupture of membranes (PPROM), and chorioamnionitis. Primary outcomes were compared between cohorts, with a p-value of < 0.05 denoting statistical significance. Secondary outcomes included dual twin survival rates at birth and 30 days of life, adjusting for maternal age and Quintero stage at the time of FLPC. A total of 343 cases were included (35 early laser, 308 standard laser), with demographics summarized in Table 1. As seen in Table 2, the early laser group had significantly higher rates of CAS when compared to the standard laser group [34.3% vs 13.3% of cases (p < 0.001)]. The early laser group also demonstrated higher rates of PPROM [45.7% versus 25.0% (p=0.009)] and chorioamnionitis [11.4% vs 1.3% (p=0.005)]. Cessation of amniotic fluid leakage following PPROM occurred more frequently in the early laser group [37.5% vs 3.9% (p=0.001)]. Dual twin survival differed between the early and standard groups, although not significantly so. Early FLPC for TTTS performed at 16 weeks is associated with significantly higher rates of CAS, PPROM, and chorioamnionitis. However, amniotic fluid leakage tends to stop after PPROM following early FLPC, which we speculate may help to ameliorate some adverse fetal effects. Even after adjustment for higher Quintero staging in the early laser group, twin survival does not seem to be affected.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Understanding of adopting flat-top laser in laser powder bed fusion processed Inconel 718 alloy: simulation of single-track scanning and experiment

Laser beam intensity profile used in laser powder bed fusion (LPBF) process is generally Gaussian, which may not be the best to deliver site-specific microstructures. In this study, a flat-top laser with large-size laser spot and uniform intensity distribution is adopted in the LPBF process with Inconel 718 powder. Comparison investigations are conducted to the standard Gaussian laser. Firstly, the parameters for the flat-top laser are optimized by multi-physics simulation of single tracks. Then, the thermodynamic behaviors and morphologies of the molten pool are observed combined with experiments. A cubic sample is also fabricated utilizing double-laser system to reveal the different characteristics of the resultant microstructures. The results show that the flat-top laser can work at a relatively wider range of laser power without depression, which often occurs in the case of Gaussian laser. The molten pool induced by the flat-top laser has large width-depth ratio with a flat bottom boundary, and more moderate flow in the half bottom. These features combined with the temperature and flow fields of the flat-top laser provide advantageous conditions for directional epitaxial growth of columnar grains during multi-layer fabrication. The epitaxial growth is retained and can extends to 4 mm from the single-crystal baseplate. This demonstrates great potential of LPBF with the adopted flat-top laser to be applied in fabricating or repairing components with directional crystal structures or single-crystal structures.

Monolithic, Optically Coupled, Multi-Section Mid-IR Quantum Cascade Lasers

Mid-infrared (mid-IR λ ≈ 3–12 μm), single-mode-emission Quantum Cascade Lasers (QCLs) are of significant interest for a wide range of applications, especially as the laser sources are chosen for laser absorption spectroscopy. In this work, we present the design, fabrication and characterization of multi-section, coupled-cavity, mid-IR quantum cascade lasers. The purpose of this work is to propose a design modification for a coupled-cavity device, yielding a single-mode emission with a longer range of continuous tuning during the pulse, in contrast to a 2-section device. This effect was obtained and demonstrated in the work. The proposed design of a 3-section coupled-cavity QCL allows for a single-mode emission with 35 dB side-mode suppression ratio. Additionally, the time-resolved spectra of the wavelength shift during pulse operation, show a continuous tuning of ~3 cm−1 during the 2 μs pulse. The devices were fabricated in a slightly modified, standard laser process using dry etching.

Birefringent atomic vapor laser lock in a hollow cathode lamp

We report a robust method of stabilizing a laser to the frequency of an atomic transition using a hollow cathode lamp. In contrast to the standard dichroic atomic vapor laser lock method, which uses dichroism induced by a longitudinal magnetic field, we employ birefringence induced by a transversal magnetic field. We applied this method to the ( 5 s 2 ) 1 S 0 − ( 5 s 5 p ) 1 P 1 transition (461 nm) of Sr. Although the hollow cathode is made of ferromagnetic material, we successfully applied a magnetic field of sufficient strength to obtain an error signal with a theoretical maximum slope. This method may be applied to other hollow cathode lamps of different atomic species.