Convergence of vestibular and proprioceptive signals in the cerebellar nodulus/uvula enhances the encoding of self-motion in primates.

The integration of different sensory streams is required to dynamically estimate how our head and body are oriented and moving relative to gravity. This process is essential to continuously maintain stable postural control, autonomic regulation, and self-motion perception. The nodulus/uvula (NU) in the posterior cerebellar vermis is known to integrate canal and otolith vestibular input to signal angular and linear head motion in relation to gravity.

Isolator-free 60 W diamond Raman laser at 607 nm.

We report an intra-cavity frequency doubled diamond Raman laser operating at 607 nm. A z-fold cavity design was configured to prevent back reflections into the fiber amplifier, which avoided the use of isolators in the pump beam path. A maximum output power of 60 W was generated in two output beams at an optical conversion efficiency of 28% from the 1045 nm pump.

Reduction of relative intensity noise in a diamond Raman laser.

The relative intensity noise (RIN) characteristics of a continuous-wave diamond Raman laser are investigated for the first time. The results reveal the parasitic stimulated Brillouin scattering (SBS) that usually occurred with higher-order spatial modes in the diamond Raman resonator is a pivotal factor impacting the Raman longitudinal modes and deteriorating the RIN level. The diamond Raman laser automatically switches to single-longitudinal-mode operation and the RIN level is significantly decreased in the frequency range of 200 Hz to 1 MHz after the parasitic SBS is effectively suppressed through inserting a spatial aperture or a χ nonlinear crystal into the cavity.

Secondary Raman and Brillouin mode suppression in two- and three-mirror-cavity diamond Raman lasers.

We report an investigation into secondary mode suppression in single longitudinal mode (SLM) 1240 nm diamond Raman lasers. For a three-mirror V-shape standing-wave cavity incorporating an intra-cavity LBO crystal to suppress secondary modes, we achieved stable SLM output with a maximum output power of 11.7 W and a slope efficiency 34.

Vestibular Contributions to Primate Neck Postural Muscle Activity during Natural Motion.

To maintain stable posture of the head and body during our everyday activities, the brain integrates information across multiple sensory systems. Here, we examined how the primate vestibular system, independently and in combination with visual sensory input, contributes to the sensorimotor control of head posture across the range of dynamic motion experienced during daily life. We recorded activity of single motor units in the splenius capitis and sternocleidomastoid muscles in rhesus monkeys during yaw rotations spanning the physiological range of self-motion (up to 20 Hz) in darkness.

Modeling and characterization of high-power single frequency free-space Brillouin lasers.

Free-space Brillouin lasers (BLs) are capable of generating high-power, narrow-linewidth laser outputs at specific wavelengths. Although there have been impressive experimental demonstrations of these lasers, there is an absence of a corresponding theory that describes the dynamic processes that occur within them. This paper presents a time-independent analytical model that describes the generation of the first-order Stokes field within free-space BLs.

Modulation depth and bandwidth analysis of planar thermo-optic diamond actuators.

Thermo-optic actuators based on bulk materials are considered too slow in applications such as laser frequency control. The availability of high-quality optical materials that have extremely fast thermal response times, such as diamond, present an opportunity for increasing performance. Here, diamond thermal actuators are investigated for configurations that use a planar thermal resistive layer applied to a heat-sinked rectangular prism.

Narrow laser-linewidth measurement using short delay self-heterodyne interferometry.

Delayed self-heterodyne interferometry is a commonly used technique for the measurement of laser linewidth. It typically requires the use of a very long delay fiber when measuring narrow linewidth (especially linewidths in the kHz-range) lasers. The use of long fibers can result in system losses and the introduction of 1/f noise that causes spectral line broadening.

The Influence of Noise Floor on the Measurement of Laser Linewidth Using Short-Delay-Length Self-Heterodyne/Homodyne Techniques.

Delayed self-heterodyne/homodyne measurements based on an unbalanced interferometer are the most used methods for measuring the linewidth of narrow-linewidth lasers. They typically require the service of a delay of six times (or greater) than the laser coherence time to guarantee the Lorentzian characteristics of the beat notes. Otherwise, the beat notes are displayed as a coherent envelope.

Integrated room temperature single-photon source for quantum key distribution: publisher's note.

This publisher's note contains a correction to Opt. Lett.47, 1673 (2022)10.

Integrated room temperature single-photon source for quantum key distribution.

High-purity single-photon sources (SPS) that can operate at room temperature are highly desirable for a myriad of applications, including quantum photonics and quantum key distribution. In this work, we realize an ultra-bright solid-state SPS based on an atomic defect in hexagonal boron nitride (hBN) integrated with a solid immersion lens (SIL). The SIL increases the source efficiency by a factor of six, and the integrated system is capable of producing over ten million single photons per second at room temperature.

Widely-tunable single-frequency diamond Raman laser.

We report a diamond Raman laser that is continuously-tunable across the range from 590 nm to 625 nm producing continuous wave output with up to 8 W. The system is based on an all-fiber and tunable (1020-1072 nm) Yb-doped pump laser with a spectral linewidth of 25 GHz that is Raman-shifted and frequency doubled in a cavity containing diamond and a lithium triborate second harmonic crystal. Despite the broad pump spectrum, single frequency output is obtained across the tuning range 590-615 nm.

Comprehensive Thermal Analysis of Diamond in a High-Power Raman Cavity Based on FVM-FEM Coupled Method.

Despite their extremely high thermal conductivity and low thermal expansion coefficients, thermal effects in diamond are still observed in high-power diamond Raman lasers, which proposes a challenge to their power scaling. Here, the dynamics of temperature gradient and stress distribution in the diamond are numerically simulated under different pump conditions. With a pump radius of 100 μm and an absorption power of up to 200 W (corresponding to the output power in kilowatt level), the establishment period of thermal steady-state in a millimeter diamond is only 50 μs, with the overall thermal-induced deformation of the diamond being less than 2.

Modelling and characterisation of continuous wave resonantly pumped diamond Raman lasers.

We present experimental results and modeling of continuous wave resonantly pumped Raman lasers. The first Stokes diamond Raman ring laser generated 0.6 W at 960 nm with an efficiency of 18%; the second Stokes laser generated 1.

Soleus responses to Achilles tendon stimuli are suppressed by heel and enhanced by metatarsal cutaneous stimuli during standing.

Key Points: We examined the influence of cutaneous feedback from the heel and metatarsal regions of the foot sole on the soleus stretch reflex pathway during standing. We found that heel electrical stimuli suppressed and metatarsal stimuli enhanced the soleus vibration response. Follow-up experiments indicated that the interaction between foot sole cutaneous feedback and the soleus vibration response was likely not mediated by presynaptic inhibition and was contingent upon a modulation at the ⍺-motoneuron pool level.

Quantum-randomized polarization of laser pulses derived from zero-point diamond motion.

Intrinsic randomness in quantum systems is a vital resource for cryptography and other quantum information protocols. To date, randomizing macroscopic polarization states requires randomness from an external source, which is then used to modulate the polarization e.g.

Cascaded Stokes polarization conversion in cubic Raman crystals.

We describe a theoretical approach based on Müller and tensor calculus for predicting the polarization state and gain of cascaded Stokes orders produced under coherent Raman scattering regime conditions. The formulation follows a Markovian-style implementation for F-type modes in Raman cubic crystals. The theoretical model is supported by experimental results that corroborate that the polarization and power of the cascaded Stokes orders can be effectively predicted using sequential calculus.

Lower-limb muscle responses evoked with noisy vibrotactile foot sole stimulation.

Aim: Cutaneous feedback from the foot sole contributes to the control of standing balance in two ways: it provides perceptual awareness of tactile perturbations at the interface with the ground (e.g., shifts in the pressure distribution, slips, etc.

Analysis of a thermal lens in a diamond Raman laser operating at 1.1 kW output power.

We report experimental observations of thermal lens effects in a diamond Raman laser operating up to 1.1 kW output power in a quasi- steady-state regime. Measured changes in the output beam parameters as a function of output power, including beam quality factor and beam divergence after a fixed focusing lens, are compared to modelling enabling us to track the development of a thermal lens up to 16 diopters at maximum output power.

Diamond sodium guide star laser.

Laser guide stars based on the mesospheric sodium layer are becoming increasingly important for applications that require correction of atmospheric scintillation effects. Despite several laser approaches being investigated to date, there remains great interest in developing lasers with the necessary power and spectral characteristics needed for brighter single or multiple guide stars. Here we propose and demonstrate a novel, to the best of our knowledge, approach based on a diamond Raman laser with intracavity Type I second-harmonic generation pumped using a 1018.

Broadly tunable linewidth-invariant Raman Stokes comb for selective resonance photoionization.

We demonstrate a continuously tunable, multi-Stokes Raman laser operating in the visible range (420 - 600 nm). Full spectral coverage was achieved by efficiently cascading the Raman shifted output of a tunable, frequency-doubled Ti:Sapphire laser. Using an optimized hemi-spherical external Raman cavity composed only of a diamond crystal and a single reflecting mirror, producing high power output at high conversion efficiency (>60 % from pump to Stokes) for a broad range of wavelengths across the visible.