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Vertical external-cavity surface-emitting lasers (VECSELs) augmented by intra-cavity nonlinear optical frequency conversion have emerged as an attractive light source of ultraviolet to visible light for demanding scientific applications, relative to other laser technologies. They offer high power, low phase noise, wide frequency tunability, and excellent beam quality in a simple and inexpensive system architecture. Here, we characterize the frequency stability of an intra-cavity frequency-doubled VECSEL with 690 mW of output power at 475 nm using the delayed self-heterodyne technique and direct comparison with a commercial external-cavity diode laser (ECDL). We measure the fundamental's Lorentzian linewidth to be $2\pi\times5.3(2)$ kHz, and the total linewidth to be $2\pi\times23(2)$ kHz. In addition, we perform Rydberg-state spectroscopy via electromagnetically induced transparency (EIT), observing narrow 3.5 MHz full-width half-maximum EIT. By doing so, we demonstrate that intra-cavity frequency-doubled VECSELs can perform precision spectroscopy at the MHz level, and are a promising tool for contemporary, and future, quantum technologies., Comment: 13 pages, 5 figures

OBJECTIVES The primary objective of this study was to compare a traditional green KTP laser to a new investigational yellow laser (PhotoLase) in the treatment of facial telangiectasia in terms of the treatment outcomes. The secondary objective was to assess the functionality and reliability of the PhotoLase system from the perspective of the user. STUDY DESIGN/METHODS The study was a randomized split-face double-blinded study that compared the treatment efficacy of the 532-nm KTP laser and the investigational 585-nm PhotoLase laser. One or two treatments were given based on the response of the first treatment. The improvement of telangiectasia was graded according to a 7-point Telangiectasia Grading Scale (TGS) by the subjects and blinded physicians. The subjects assessed the amount of pain during the treatments using Visual Analogue Scale (VAS), and evaluated adverse effects 2-3 days after the treatment(s) using a self-assessment form. RESULTS At least 50% improvement was seen in 15/18 subjects after the first PhotoLase treatment, and a similar result was observed for KTP, as assessed by the blinded physicians (P = 0.29). In the subjects' assessment, 7/18 subjects had at least 50% improvement after the first PhotoLase treatment, whereas at least 50% improvement was observed for 10/18 subjects in the KTP side, the difference being significant (P = 0.008). The amount of pain was higher with PhotoLase compared to KTP (67.7 vs. 34.6, P

We report a compact high-power yellow laser system for the treatment of cutaneous vascular lesions, such as telangiectasia and port wine stains. The system is based on optically pumped vertical-external-cavity surface-emitting lasers (VECSELs), which have emerged as an attractive alternative to solid-state and dye lasers due to their enhanced functionality and broad wavelength coverage. The reported system is capable of delivering up to 8 W of output power at ∼590 nm and includes a handheld scanner for an easy delivery of light onto the skin. The scan area can be varied from a single spot (1.4-mm diameter) up to 49 spots covering an area of 1 cm2. Additional features include adjustable fluence (0–52 J/cm2), scan patterns (line, square, hexagon), and pulse length (10–100 ms). The system has been qualified for and is currently used in a clinical trial concerning the treatment of facial telangiectasia (ClinicalTrials.gov Identifier: NCT03472859). Preliminary results of the test are reported indicating reduced treatment time for the yellow system and power reserve that could lead to further increase of the area treated in a single scan.

We report a high-power optically-pumped vertical-external-cavity surface-emitting laser emitting at around 1180 nm. The free-running laser produced 72 W of output power at a heatsink temperature of 0°C and 53 W near room temperature (20°C). The GaAs-based gain mirror was bonded to a 2-mm-thick diamond attached to a TEC-cooled copper mount in order to enable efficient heat extraction for high-power operation. Moreover, the spectrum of the laser was narrowed down to 0.06 nm by employing a combination of a birefringent filter and an etalon inside the cavity which yielded a maximum of 19 W at a heatsink temperature of 20°C. The demonstration opens a new perspective for the realisation of sodium laser guide star adaptive optics employing frequency doubling of 1180 nm radiation.

Many quantum technology applications, such as quantum information processing, precision metrology, and atomic clocks, rely on lasers at many different wavelengths with demanding characteristics in terms of power, linewidth, beam quality, and intensity noise. These lasers are typically used to detect or change the quantum states of neutral atoms and ions. Besides the need for precisely defined features fitting a specific atom/ion system, there is an increasing need to make such lasers more affordable, as well as easier to use and tailor, in order to ensure faster transit from lab to real applications [1].

The primary objective of this study was to compare a traditional green KTP laser to a new investigational yellow laser (PhotoLase) in the treatment of facial telangiectasia in terms of the treatment outcomes. The secondary objective was to assess the functionality and reliability of the PhotoLase system from the perspective of the user.The study was a randomized split-face double-blinded study that compared the treatment efficacy of the 532-nm KTP laser and the investigational 585-nm PhotoLase laser. One or two treatments were given based on the response of the first treatment. The improvement of telangiectasia was graded according to a 7-point Telangiectasia Grading Scale (TGS) by the subjects and blinded physicians. The subjects assessed the amount of pain during the treatments using Visual Analogue Scale (VAS), and evaluated adverse effects 2-3 days after the treatment(s) using a self-assessment form.At least 50% improvement was seen in 15/18 subjects after the first PhotoLase treatment, and a similar result was observed for KTP, as assessed by the blinded physicians (P = 0.29). In the subjects' assessment, 7/18 subjects had at least 50% improvement after the first PhotoLase treatment, whereas at least 50% improvement was observed for 10/18 subjects in the KTP side, the difference being significant (P = 0.008). The amount of pain was higher with PhotoLase compared to KTP (67.7 vs. 34.6, P 0.001). There was no difference in the frequency of erythema, crusting or purpura between the devices, but more blistering and less edema were seen after PhotoLase treatment (P 0.05). Treatment with PhotoLase was evaluated to be 4.7-fold faster than with KTP and the PhotoLase system was more compact, narrower, lighter, and easier to carry than KTP.The investigational PhotoLase laser enables significantly faster treatments, but the process is somewhat more painful than with KTP, otherwise providing a similar clinical outcome in the treatment of facial telangiectasia. Treatment Protocol Lasers Surg. Med. 51:223-229, 2019. © Wiley Periodicals, Inc.

Semiconductor disk lasers (SDLs), also known as optically pumped vertical external-cavity surface-emitting lasers (VECSELs), offer unparalleled features combining high beam quality, large wavelength coverage, multi-watt output power, narrow linewidth, and broad tuning range. Moreover, relative to the features they provide, SDLs are compact and cost-effective systems. Their unique properties have already been recognized in biophotonics, for example, in photocoagulation treatment of macular degeneration using yellow radiation and multiphoton imaging, yet their full spread to applications is still to come. This chapter provides an overview of key technology concepts related to SDLs and a summary of the most important developments in terms of wavelength coverage and output powers. Specific developments are presented for SDLs emitting continuous wave (CW) radiation at the yellow-orange-red optical spectrum and for SDLs emitting picosecond pulses at red wavelengths. The chapter is concluded with a review of several biophotonics applications and their needs for laser sources, which are then put in a perspective of current SDL achievements.

The first monolithic GaAs-based vertical-external-cavity surface-emitting laser (VECSEL) operating at 1550 nm is reported. The VECSEL operation is based on a gain mirror which was grown in a single growth run by plasma-assisted molecular beam epitaxy. The gain mirror comprised eight GaInNAsSb/GaAs quantum wells with a photoluminescence peak at 1505 nm and an AlAs/GaAs distributed Bragg reflector ensuring high reflectivity. The VECSEL chip was pumped with an 808-nm diode laser that had a large quantum defect in respect to the lasing wavelength. An output power of 80 mW in continuous wave mode and 210 mW in pulsed pump mode are demonstrated close to room temperature.

We report on a frequency-doubled VECSEL emitting at 512.6 nm. The laser spectrum was narrowed with a Volume Bragg Grating and the intracavity frequency-doubling was achieved with a periodically poled MgO-doped lithium niobate.

We report on a frequency doubled vertical-external-cavity surface-emitting laser emitting 5.6 W at 635 nm. The cavity employed a wafer-fused AlInGaAs/InP-AlAs/GaAs gain mirror in a V-shaped configuration. The heatsink temperature was 20 °C.

The main concepts and recent results underpinning the rapid development of vertical-external-cavity surface-emitting lasers (VECSELs) are reviewed. In particular, we focus on developments addressing new wavelength domains and emerging applications.

We demonstrate an OP-VECSEL prototype emitting more than 6W of CW output power at 625 nm. We employ dilute nitride (GaInNAs) quantum wells emitting fundamentally at 1250 nm together with intracavity frequency doubling. submittedVersion

A high-power optically-pumped vertical-external-cavity surface-emitting laser (VECSEL) generating 10.5 W of cw output power at 615 nm is reported. The gain mirror incorporated 10 GaInNAs quantum wells and was designed to have an emission peak in the 1230 nm range. The fundamental emission was frequency doubled to the red spectral range by using an intra-cavity nonlinear LBO crystal. The maximum optical-to-optical conversion efficiency was 17.5%. The VECSEL was also operated in pulsed mode by directly modulating the pump laser to produce light pulses with duration of ~1.5 µs. The maximum peak power for pulsed operation (pump limited) was 13.8 W. This corresponded to an optical-to-optical conversion efficiency of 20.4%.

We report a high-power VECSEL emitting

We report on the development of a high-power vertical-external-cavity surface-emitting laser (VECSEL) emitting around 1180 nm. The laser emitted 50 W of output power when the mount of the gain chip was cooled to -15°C. The output power was measured using a 97% reflective cavity end-mirror. The VECSEL was arranged to form an I-shaped cavity with a length of ~100 mm; the gain chip and a curved dielectric mirror (RoC=150) acting as cavity end mirrors. The gain chip was grown by molecular beam epitaxy (MBE) and incorporated 10 GaInAs/GaAs quantum wells. For efficient heat extraction, the chip was capillary bonded to a diamond heat spreader which was attached to a TEC-cooled copper mount. The maximum optical-to-optical conversion efficiency of 28% was achieved for 42 W of output power and -15°C mount temperature.

We report the first monolithic GaAs-based vertical external-cavity surface-emitting laser (VECSEL) operating at 1550 nm. The VECSEL is based on a gain mirror which was grown by plasma-assisted molecular beam epitaxy and comprises 8 GaInNAsSb/GaAs quantum wells and an AlAs/GaAs distributed Bragg reflector. When pumped by an 808 nm diode laser, the laser exhibited an output power of 80 mW for a mount temperature of 16 °C.

We report on the development of a pulsed high-power frequency doubled vertical-external-cavity surface-emitting laser (VECSEL) with a peak output power of 14 W and emission spectrum near 588 nm. The semiconductor gain chip was grown by molecular beam epitaxy and comprised 10 GaInAs quantum wells. The gain structure was designed to be antiresonant at 1180 nm. The fundamental wavelength was frequency doubled to the yellow–orange spectral range using a 10-mm long critically phase matched lithium triborate nonlinear crystal, situated at the mode waist of the V-shaped laser cavity. The emission spectrum was narrowed down to FWHM of < 0.2 nm by employing a 1.5 mm birefringent filter and a 100-μm-thick etalon inside the cavity. By directly modulating the pump laser of the VECSEL, we were able to produce pulse widths down to 570 ns with average and peak output power of 81 mW and 14 W, respectively. The repetition rate was kept constant at 10 kHz throughout the measurements. The maximum peak power obtained was pump power limited. In comparison, at the same coolant temperature, a maximum of 8.5 W was achieved in continuous wave. The maximum optical-to-optical conversion efficiency (absorbed peak pump power to peak output power) was calculated to be 20–21 %.

We report on the use of a Semiconductor Disk Laser (SDL) as a seed laser for an Ytterbium-Doped Photonic Bandgap Fiber (Yb-PBGF) amplifier in a Master-Oscillator Power-Amplifier (MOPA) configuration. The SDL comprised a GaInAs/GaAs/GaAsP gain chip, a 1-mm-thick etalon for mode selection, and a 3-mm-thick birefringent filter for wavelength tuning. The fiber amplifier consisted of an Yb-doped core surrounded by a structure of periodically arranged germanium rods with a pitch of 10.2 μm, and to maintain the polarization, the fiber comprised two boron rods. The output of the MOPA-configuration was 31 W and the linewidth of the amplifier output was 149±31 kHz.

We report on the development of a high-efficiency frequency doubled vertical-external-cavity surface-emitting laser with an output power of 20 W and emission spectrum centered at 588 nm. The MBE-grown gain chip incorporated 10 GaInAs quantum wells and emitted in the 1180 nm range. The frequency conversion was achieved using a lithium triborate nonlinear crystal in an intra-cavity configuration. In addition to the nonlinear crystal, the V-shaped cavity also included a birefringent filter and an etalon for linewidth narrowing and wavelength tuning. The maximum optical-to-optical conversion efficiency obtained was ~28 % for 16 W of output power and the VECSEL had a tuning bandwidth of ~26 nm ranging from about 576 to 602 nm. We were also able to generate yellow pulses down to 570 ns duration by directly modulating the VECSEL’s pump laser.

We review our results concerning the development of Semiconductor Disk Lasers with emission wavelength in the range of 1100-1200 nm. In particular, we highlight our recent demonstrations of SDLs with an output power of more than 20 W for emission around 1180 nm and corresponding frequency doubled power of more than 10 W at around 589 nm. The SDL gain chips utilize either dilute nitride (GaInNAs) or low-temperature GaInAs quantum wells.

We report a high power single-frequency 1178 nm laser combining an optically-pumped semiconductor disk laser and an Yb-doped photonic bandgap fiber amplifier. An output power of 31 W with

In this paper we report the development of an intra-cavity frequency doubled high power VECSEL emitting around 589 nm.

Photodynamic therapy (PDT) with porphyrins and red light (610–630nm) is finding increasing clinical application for both the eradication of relatively small tumors and the palliation of inoperable or obstructive tumors. PDT also shows some promise for the sterilization of the tumor bed after surgical removal of neoplastic masses.Opticallypumpedvertical external-cavity surface-emitting lasers (VECSELs) appear to be a very innovative and efficient technology in this specificwavelength range. Furthermore, VECSELs are power scalable and wavelength tunable, and are an appealing light source for PDT.We report a VECSEL emittingmore than 8Wof output power at around 615nm. The VECSEL was designed to emit at a fundamental wavelength of 1230nm by using GaInNAs/GaAs quantum wells. The cavity had a V-shaped geometry and incorporated a LBO-crystal for frequencydoubling to the red spectral range. The cavity also included an etalon and a birefringent filter forwavelength control. Thewavelengthwas tunableover a rangeof∼20nm. Additional developments including, wavelength extension, pulsed operation and construction of compact prototypes will also be presented.

A high-efficiency optically pumped vertical-external-cavity surface-emitting laser emitting 20 W at a wavelength around 588 nm is demonstrated. The semiconductor gain chip emitted at a fundamental wavelength around 1170-1180 nm and the laser employed a V-shaped cavity. The yellow spectral range was achieved by intra-cavity frequency doubling using a LBO crystal. The laser could be tuned over a bandwidth of ~26 nm while exhibiting watt-level output powers. The maximum conversion efficiency from absorbed pump power to yellow output was 28% for continuous wave operation. The VECSEL's output could be modulated to generate optical pulses with duration down to 570 ns by directly modulating the pump laser. The high-power pulse operation is a key feature for astrophysics and medical applications while at the same time enables higher slope efficiency than continuous wave operation owing to decreased heating.

The treatment of superficial vascular lesions on skin are among the most common sought-after dermatological laser procedures. The treatment method is based on the absorption of laser light by haemoglobin in blood, which results in the transfer of heat and wanted vessel wall damage. The yellow wavelength range is considered ideal for this purpose, because of the high absorption peak of haemoglobin around 577 nm. However, the yellow spectral range is challenging for any laser technology to produce, which is why there are only a few options on the market, notably the pulsed dye laser (PDL), resulting in limited and expensive treatments.

We report high power single-frequency vertical external-cavity surface-emitting lasers (VECSELs)for applications in atomic, molecular and optical (AMO)physics. The laser platform is wavelength versatile, delivering watt-level output between 920 nm to 1260 nm in single-mode.