Recent developments in the field of quantum research call for single frequency lasers (SFL) with narrow linewidth and extremely low noise. The accuracy, long coherence length, and stability of power allow these SFLs to provide a precise transition between energy levels, which is required in quantum applications, such as quantum computing, quantum metrology, optical atomic clocks, and ion cooling. Here we report on a compact all-fiber single-frequency distributed Bragg reflector (DBR) laser operating at 871 nm. Single longitudinal and transverse mode laser output was obtained with the use of 3 cm 1 wt% Neodymium Nd3+ doped phosphate fiber as a gain medium. A power of 6.7 mW and a slope efficiency of 3.3% with respect to the launched pump were obtained. The obtained power was limited by the launched pump power into the cavity. The obtained beam was highly polarized with a polarization extension ratio of 29 dB. This laser was later frequency doubled in-fiber coupled long periodically poled Lithium Niobate waveguide resulting in a 435.5nm laser required for a Yb+ clock.

Robust and reliable high-power, low-noise, narrow-linewidth fiber laser sources are in great demand for many advanced applications. Thermal effects always impose an obstacle for the power scaling of a single-frequency laser oscillator. Reducing the quantum defect of a single-frequency fiber laser is a promising approach to a high-power, low-noise, narrow-linewidth laser source. We present our experimental investigations toward high-power, lowquantum-defect (LQD), single-frequency distributed Bragg reflector (DBR) fiber laser oscillators operating at 1030 nm. An output power of 1.4 W was achieved with a 3 cm 20 wt% Yb3+-doped phosphate fiber pumped at 1014 nm.

Optical refrigeration has significant promise for vibration-free cryogenic cooling and radiation-balanced fiber lasers. In this paper, we report theoretical and experimental investigations of optical refrigeration in thulium (Tm3+) doped indium fluoride glass (Tm3+:InF3) from room temperature. Comprehensive spectroscopic studies of Tm3+:InF3 were conducted, and its cooling with 1875, 1900, and 1950 nm pump lasers at different power levels has been measured. Maximum cooling of 2.4 K was achieved with 4.4 W from a 1900 nm laser. The experimental results agree with our theoretical expectations. Our experiment has demonstrated that Tm3+:InF3 has better cooling efficiency than Tm3+ doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass due to Tm-3+:InF3's lower maximum phonon energy, which reduces non-radiative decay.

High-power single-frequency laser oscillators, ranging from tens to even hundreds of watts, are in high demand for specialized applications such as quantum information processing and laser interferometer gravitational-wave observatories. In this paper, we present numerical investigations into the power scalability of single-frequency distributed Bragg reflector (DBR) ytterbium (Yb3+)-doped phosphate fiber lasers. We propose a low quantum defect (QD) operational approach to achieve 10-watt single-frequency laser oscillators, optimized using a figure of merit defined as the ratio of laser efficiency to quantum defect. Additionally, we report preliminary experimental investigations into the power scaling of low-QD Yb3+-doped phosphate fiber lasers.

Spectroscopic studies on Yb3+ and Dy3+ co-doped, and Yb3+, Er3+, and Dy3+ triple-doped ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) glasses are reported. Efficient energy transfers from Yb3+ directly to Dy3+, and from Yb3+ to Er3+ and then from Er3+ to Dy3+ are demonstrated, and their rates are calculated from the measured lifetimes. This discovery enables the development of high-power Dy3+ doped fiber lasers pumped by low-cost, high-efficiency InGaAs diodes within the ytterbium absorption band.

Low quantum defect single-mode 1030 nm Ytterbium (Yb3+)-doped phosphate fiber lasers were investigated, achieving a 4.41 W output through core-pumping with a home-built single-mode 1018 nm Yb3+-doped silica fiber laser.

High-power single-frequency laser oscillators are in great demand for some specific applications, such as quantum information and laser interferometer gravitational-wave observatories, where 10-watt or even 100-watt-level narrow-linewidth lasers with extremely low noise levels are required. In this paper, we present numerical investigations on the power scalability of single-frequency distributed Bragg reflector (DBR) ytterbium-doped phosphate fiber lasers and identify the low-quantum-defect operation approach to 10-watt single-frequency laser oscillators with the best figure of merit, defined by the ratio of the laser efficiency to the quantum defect. This research offers valuable insights for the design and development of high-power single-frequency DBR fiber laser oscillators at many other wavelengths. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

An ultra-low quantum defect (< 0.6%) linearly polarized single frequency fiber laser was demonstrated. To mitigate thermal effects, pump wavelength optimization has been performed in order to study the effect of quantum defects on laser performance.

In recent years, there has been a dramatically increasing demand for high-performance narrow-linewidth lasers for optical atomic clock and quantum applications. In this paper, we report on a single-frequency distributed Bragg reflector fiber laser operating at 871 nm that can be used to produce a 435.5 nm narrow-linewidth laser for a Yb+ clock via second-harmonic generation. Linearly polarized single-longitudinal-mode laser output with a power of 6.7 mW and a polarization extinction ratio of 29 dB was obtained by using a 3-cm long 1 wt. % neodymium (Nd3+)-doped phosphate fiber as the gain fiber.

A single-frequency distributed-Bragg-reflector fiber laser at 980 nm with a quantum defect of less than 0.6% was developed with a 1.5-cm 12 wt% ytterbium-doped phosphate fiber pumped by a 974.5-nm laser diode. Linearly polarized single-longitude-mode laser with a polarization extinction ratio (PER) of nearly 30 dB and spectral linewidth of less than 1.8 kHz was obtained. A maximum output power of 275 mW was measured at a launched pump power of 620 mW. The performance of the single-frequency fiber laser pumped at 909 nm and 976 nm was also characterized. This research demonstrated an approach to high-power single-frequency fiber laser oscillators with mitigated thermal effects.

Uncoupled multicore fibers are promising platforms for advanced optical communications, optical computing, and novel laser systems. In this paper, an injection-locked highly ytterbium (Yb3+)-doped uncoupled-61-core phosphate fiber laser at 1030 nm is reported. The 61-core fiber with a core-to-core pitch of 20 μm was fabricated with the stack-and-draw technique. Each core doped with 6-wt.% Yb3+ ions has a diameter of 3 μm and numerical aperture of 0.2. Linearly polarized single-frequency output of 9.1 W was obtained from the injection-locked cavity with a 10-cm-long gain fiber at a pump power of 23.6 W. The injection locking of all 61 cores was confirmed by inspecting the longitudinal modes of the individual lasers with a scanning Fabry-Perot interferometer. The performance of the injection-locked 61-core fiber laser was characterized and compared to that of the free-running operation in terms of optical spectrum, near- and far-field intensity profiles, and relative intensity noise.

Clinical relevanceCurrently eye examinations are usually based on autorefraction followed by subjective refraction (SR) with a phoropter. An automated phoropter that can also perform autorefraction may facilitate the optometric workflow.BackgroundThe efficiency and feasibility of an objective autorefraction and correction system are assessed by comparing objective refractive measurements with SR on the same subjects and evaluating the visual acuity (VA) values obtained after the objective refractive measurement and correction.MethodsObjective autorefraction and correction was performed on 41 subjects using an automated binocular phoropter system. The auto-phoropter performs autorefraction by wavefront measurement and corrects the spherical and cylindrical errors with tunable fluidic lenses while the patient looks at a visual display inside the instrument. The instrument outputs are optometric constants of spherical and cylindrical aberrations. After measurement and automated correction of the refractive errors, the VA values were assessed by having the subjects look at an integrated Snellen chart. The objective measurement results were statistically compared with their SR.ResultsThe correlations between SR and objective autorefraction and correction spherical equivalents (M) were 0.98 (0.97-0.99) and 0.96 (0.93-0.98), the vertical Jackson cross cylinder (J0) were 0.96 (0.92-0.98) and 0.95 (0.91-0.97), and the oblique Jackson cross cylinder (J45) were 0.73 (0.55-0.85) and 0.82 (0.69-0.90), for the right and left eyes, respectively, with the 95% confidence interval (CI) values in parentheses. 89.0% of the 82 eyes had at least 6/7.5 VA.ConclusionsA significant agreement between the SR and objective autorefraction and correction was observed. An all-objective refractive assessment with instantaneous verification may improve the precision of eye prescriptions and possibly reduce the procedure time.

Compact and robust linearly-polarized pulsed laser sources at 976 nm are in great demand for high-efficiency harmonic generation of blue and deep ultraviolet lasers. In this paper, we report a semiconductor saturable absorber mirror mode-locked fiber ring-cavity laser at 976 nm, in which only 2.4 cm highly ytterbium-doped phosphate fiber was used as the gain fiber. Fundamental mode-locking operation with 5-ps pulses at a repetition rate of 16.53 MHz and with average output power of 2 mW was obtained at a pump power of 215 mW. The pulse energy and peak power of the mode-locked pulses were estimated to be 0.12 nJ and 24.4 W, respectively. The polarization extinction ratio was measured to be 21.5 dB.

We present the performance analysis and specifications of a portable auto-phoropter system that can be employed for fast refractive assessment of a large population. A customized Shack-Hartmann wavefront sensor is developed to accurately measure the defocus and astigmatism of the eye within ±10D and ±6D, respectively. Three fluidic lenses are designed to correct the vision in real time. A digital Snellen chart is integrated into the system to validate the accuracy of the measurement and the correction by means of achieving 20/20 vision. The refractive error of eight subjects (16 eyes) has been measured objectively (without patient's feedback) using the proposed system and the results are compared with their clinical prescription through the Bland-Altman method. It is shown that the auto-phoropter takes less than 8 s to measure and correct the eye refractive error with an accuracy of ±0.25D.

In this paper, we present the demonstration of a 10-W level picosecond Yb 3+ -doped master oscillator and power amplifier at 976 nm in all-fiber configuration. A linear-cavity Yb 3+ -doped fiber laser mode-locked by a semiconductor-saturable-absorber-mirror was developed as the seed laser with a pulse width of 10.9 ps operating at a repetition rate of 34.1 MHz. The average power of the picosecond mode-locked laser was amplified to 8.1 W by two core-pumped pre-amplifiers and two cladding-pumped power amplifiers. The pulse width of the output mode-locked laser was measured to be 15.6 ps and its pulse energy is 237.5 nJ, corresponding to a peak power of 15.2 kW. The polarization extinction ratio and beam quality (M 2 ) of this 10-watt-level mode-locked laser were measured to be 13 dB and 1.2, respectively.

Quantum receivers aim to effectively navigate the vast quantum-state space to endow quantum information processing capabilities unmatched by classical receivers. To date, only a handful of quantum receivers have been constructed to tackle the problem of discriminating coherent states. Quantum receivers designed by analytical approaches, however, are incapable of effectively adapting to diverse environmental conditions, resulting in their quickly diminishing performance as the operational complexities increase. Here, we present a general architecture, dubbed the quantum receiver enhanced by adaptive learning, to adapt quantum receiver structures to diverse operational conditions. The adaptively learned quantum receiver is experimentally implemented in a hardware platform with record-high efficiency. Combining the architecture and the experimental advances, the error rate is reduced up to 40% over the standard quantum limit in two coherent-state encoding schemes.

Single-frequency fiber lasers with extremely low noise and narrow spectral linewidth have found many scientific and practical applications. There is great interest in developing single-frequency fiber lasers at new wavelengths. In this paper, we report a single-frequency Nd3+-doped phosphate fiber laser operating at 880 nm, which is the shortest demonstrated wavelength for a single-frequency fiber laser thus far, to the best of our knowledge. An output power of 44.5 mW and a slope efficiency of 20.4% with respect to the absorbed pump power were obtained with a 2.5-cm-long 1 wt.% Nd3+-doped phosphate fiber. Our simulation results show that higher single-frequency laser output can be achieved with 1.5 wt.% or 2 wt.% Nd3+-doped phosphate fiber with mitigated ion clustering.

Photorefractive materials are capable of reversibly changing their index of refraction upon illumination. That property allows them to dynamically record holograms, which is a key function for developing an updateable holographic 3D display. The transition from inorganic photorefractive crystals to organic polymers meant that large display screens could be made. However, one essential figure of merit that needed to be worked out first was the sensitivity of the material that enables to record bright images in a short amount of time. In this review article, we describe how polymer engineering was able to overcome the problem of the material sensitivity. We highlight the importance of understanding the energy levels of the different species in order to optimize the efficiency and recording speed. We then discuss different photorefractive compounds and the reason for their particular figures of merit. Finally, we consider the technical choices taken to obtain an updateable 3D display using photorefractive polymer. By leveraging the unique properties of this holographic recording material, full color holograms were demonstrated, as well as refreshing rate of 100 hogels/second.