Phonon lasers are extensively researched as mechanical counterparts to optical lasers for various applications. An optical tweezer phonon laser was developed, but it only affected one degree of movement. To address this, we introduced a multimode levitated nanoparticle to transfer coherence between different oscillation directions. Coupling was achieved by rotating the asymmetric optical potential via trap laser polarization rotation. The change in power spectral density showed the feature of lasing transfer before and after coupling, and the mean phonon number of the system was saturated. Coherence was confirmed by measuring second-order auto-correlation function of the oscillation modes. Coupled laser systems have potential in precision measurement and quantum information processing.
Negatively charged nitrogen-vacancy (NV-) centers in diamond have a plethora of potential applications in quantum systems, including sensing and computing1-3. Photothermal heating can limit the utility of NV- center nanodiamonds, especially under high laser irradiances4-6. A composite of nanodiamonds with NV- defects and ytterbium-doped cubic sodium yttrium fluoride (Yb:α-NaYF4 or NaYF) could offset the photothermal heating of nanodiamonds by the anti-Stokes fluorescence cooling of Yb3+ ions7. We present a novel preparation method for generating a NV- diamond NaYF composite material based on a hydrothermal synthesis approach. Particle size was determined to be 230 ± 90 nm by SEM, and DLS data show a permanent connection between nanodiamonds and NaYF. Nanodiamonds are observed on the surfaces of NaYF materials. Nanodiamonds may also be incorporated within the body of individual NaYF grains, however the question of whether nanodiamonds are fully incorporated into the host NaYF material remains to be answered. The temperatures of host material and NV- defects are accessed using mean fluorescence wavelength shifts and Debye-Waller factor thermometry respectively. The obtained temperature changes with increasing 1020 nm irradiance show good agreement. Two data sets showed photothermal heating of around 10 and 13 K at 6.3 MW/cm2. Increased particle smoothness and sizes could lead to coolable composite materials.
Optically trapped nanoparticles can be used to explore heat conduction in gases. Heat conduction can be modeled using Fourier’s law when the mean-free path (MFP) of the gas molecules is short compared to the size of the heat source. When the MFP of the gas is larger than the size of the heated nanoparticle a nanoscopic approach which considers the gas’s interactions is needed. We use nanodiamonds with nitrogen-vacancy centers to measure the temperature of a trapped nanoparticle and observe both continuum (Fourier) and sub-continuum regions of heat conduction and the transition between them.
Hexagonal sodium yttrium fluoride (β-NaYF) is a promising material for optical refrigeration due to the narrow crystal field splitting of the Yb(III) ion. However, growing single crystals of β-NaYF remains a challenge due to thermal expansion stresses during melt growth. We demonstrate a hydrothermal synthesis of β-NaYF with widely tunable aspect ratios that match computationally predicted cavity resonances. The β-NaYF microcrystals contain 10% Yb(III) cations and are used to build optomechanical laser-refrigeration cantilever devices. Laser refrigeration of these devices shows cooling up to 12.5°C, which is measured using the cantilever’s fundamental eigenfrequency and photoluminescence from the Yb(III) ions.
Optically levitated nanoparticles provide excellent systems to sense minute forces and explore quantum effects in a large system. However, optically levitated nanoparticles are prone to heating and require cooling and temperature stabilization to reach sensitivities necessary to study small forces and quantum effects. This problem can be solved by trapping nanocrystals doped with rare-earth ions that can be anti-Stokes cooled by tens of degrees. The efficiency of the anti-Stokes depends on gas pressure and can counter heating due to optical absorption. Cooling nanocrystals allows for thermally stabilizing nanocrystal systems to measure minute forces and quantum effects.
We report the development of a phonon laser based on the center-of-mass oscillation of an optically levitated silica nanosphere in a free-space optical dipole trap. A parametric feedback scheme based on the detection of the oscillator’s center-of-mass is used to provide a cooling signal that intrinsically depends on the oscillator’s mean phonon occupation. When an amplification signal is added to the feedback at the mechanical resonance, these two signals produce center-of-mass dynamics that are analogous to those of a single-mode optical laser. Observed phenomena include a threshold in oscillation amplification, a transition from Brownian motion below threshold to coherent oscillation above threshold, reduction in the linewidth of the oscillation spectrum, and gain saturation. We also analyze the statistical phonon number distributions above and below threshold. The observed dynamics are described by a model that includes both stimulated and spontaneous emission of center-of-mass phonons. Importantly, the operation of this phonon laser relies on externally controllable, feedback-based parameters and therefore allows tuning of the threshold via these parameters. We also explore the use of the levitated nanoparticle phonon laser as a detector of weak external forces via injection locking.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.