We demonstrate the optical generation of dynamic dark optical ring lattices, which do not require Laguerre-Gauss beams, large optical coherence lengths or interferometric stability. Simple control signals lead to spatial modulation and reproducible rotation, offering manifold possibilities for complex dynamic ring lattices. In conjunction with a magnetic trap, these scanned 2D intensity distributions from a single laser beam will enable precision trapping and manipulation of ultracold species using blue-detuned light. The technique is ideal for azimuthal ratchet, Mott insulator and persistent current experiments with quantum degenerate gases.
We propose a tomographic method to reconstruct the optical properties of a highly-scattering medium from incoherent acousto-optic measurements. The method is based on the solution to an inverse problem for the diffusion equation and makes use of the principle of interior control of boundary measurements by an external wave field.
We present a laser beam shaping method using acousto-optic deflection of light and discuss its application to dipole trapping of ultracold atoms. By driving the acousto-optic deflector with multiple frequencies, we generate an array of overlapping diffraction-limited beams that combine to form an arbitrary-shaped smooth and continuous trapping potential. Confinement of atoms in a flat-bottomed potential formed by a laser beam with uniform intensity over its central region confers numerous advantages over the harmonic confinement intrinsic to Gaussian beam dipole traps and many other trapping s…
Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable new acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with periods as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membra…
Using acoustooptic (AO) cells based on TeO2 crystal and silica glass, we have experimentally shown for the first time that the intensity profile and the phase structure of the vortex beam are preserved under AO Bragg diffraction. As a result, the vortex beam can be deflected due to AO diffraction, whereas the acoustooptically operated vortex beams can be efficiently used in such novel branches of optical technology as optical trapping and controlled addressing of the beams with different orbital angular momentums.
We propose an original adaptive wavefront holographic setup based on the photorefractive effect (PR), to make real-time measurements of acousto-optic signals in thick scattering media, with a high flux collection at high rates for breast tumor detection. We describe here our present state of art and understanding on the problem of breast imaging with PR detection of the acousto-optic signal.
Acousto-optical coherence tomography (AOCT) consists in using random phase jumps on ultrasound and light to achieve a millimeter resolution when imaging thick scattering media. We combined this technique with heterodyne off-axis digital holography. Two-dimensional images of absorbing objects embedded in scattering phantoms are obtained with a good signal-to-noise ratio. We study the impact of the phase modulation characteristics on the amplitude of the acousto-optic signal and on the contrast and apparent size of the absorbing inclusion.
We present a photon noise and diffraction limited imaging method combining the imaging laser and ultrasonic waves. The laser optical feedback imaging (LOFI) technique is an ultrasensitive imaging method for imaging objects through or embedded within a scattering medium. However, LOFI performances are dramatically limited by parasitic optical feedback occurring in the experimental setup. In this work, we have tagged the ballistic photons by an acousto-optic effect in order to filter the parasitic feedback effect and to reach the theoretical and ultimate sensitivity of the LOFI technique. We pre…
Electrically driven acousto-optic devices that provide beam deflection and optical frequency shifting have broad applications from pulse synthesis to heterodyne detection. Commercially available acousto-optic modulators are based on bulk materials and consume Watts of radio frequency power. Here, we demonstrate an integrated 3-GHz acousto-optic frequency shifter on thin-film lithium niobate, featuring a carrier suppression over 30 dB. Further, we demonstrate a gigahertz-spaced optical frequency comb featuring more than 200 lines over a 0.6-THz optical bandwidth by recirculating the light in an…
We exercise rapid and fine control over the phase of light by transferring digitally gen- erated phase jumps from radio frequency (rf) electrical signals onto light by means of acousto-optic interaction. By tailoring the statistics of phase jumps in the electrical signal and thereby engineering the optical phase noise, we manipulate the visibil- ity of interference fringes in a Mach-Zehnder interferometer that incorporates two acousto-optic modulators. Such controlled dephasing finds applications in modern experiments involving the spread or diffusion of light in an optical network. Further, w…
We present a rigorous procedure for evaluating the photoelastic coefficients of a layered medium where the periodicity is smaller than the wavelengths of all optical and acoustic fields. Analytical expressions are given for the coefficients of a composite material comprising thin layers of optically isotropic materials. These coefficients include artificial contributions that are unique to structured media and arise from the optical and mechanical contrast between the constituents. Using numerical examples, we demonstrate that the acousto-optic properties of layered structures can be enhanced …
To achieve a distributed reflectivity measurement along an optical fiber, we develop a simplified cost-effective configuration of optical correlation- (or coherence-) domain reflectometry based on a synthesized optical coherence function by sinusoidal modulation. By excluding conventional optical heterodyne detection (practically, without using an acousto-optic modulator) and by exploiting the foot of the Fresnel reflection spectrum, the electrical bandwidth required for signal processing is lowered down to several megahertz. We evaluate the basic system performance and demonstrate its high-sp…
We demonstrate a collinear acousto-optic modulator in a suspended film of lithium niobate employing a high-confinement, wavelength-scale waveguide. By strongly confining the optical and mechanical waves, this modulator improves by orders of magnitude a figure-of-merit that accounts for both acousto-optic and electro-mechanical efficiency. Our device demonstration marks a significant technological advance in acousto-optics that promises a novel class of compact and low-power frequency shifters, tunable filters, non-magnetic isolators, and beam deflectors.
We demonstrate acousto-optic phase modulators in X-cut lithium niobate films on sapphire, detailing the dependence of the piezoelectric and optomechanical coupling coefficients on the crystal orientation. This new platform supports highly confined, strongly piezoelectric mechanical waves without suspensions, making it a promising candidate for broadband and efficient integrated acousto-optic devices, circuits, and systems.
Acousto-Optical Coherence Tomography (AOCT) is variant of Acousto Optic Imaging (called also ultrasonic modulation imaging) that makes possible to get z resolution with acoustic and optic Continuous Wave (CW) beams. We describe here theoretically the AOCT e ect, and we show that the Acousto Optic tagged photons remains coherent if they are generated within a speci c z region of the sample. We quantify the z selectivity for both the tagged photon eld, and for the M. Lesa re et al. photorefractive signal.
Acousto-Optical Coherence Tomography (AOCT) is a variant of Acousto Optic Imaging (also called Ultrasound modulated Optical Tomography) that makes possible to get resolution along the ultrasound propagation axis $z$. We present here new AOCT experimental results, and we study how the $z$ resolution depends on time step between phase jumps $T_ϕ$, or on the correlation length $Δz$. By working at low resolution, we perform a quantitative comparison of the $z$ measurements with the theoretical Point Spread Function (PSF). We present also images recorded with different $z$ resolution, and we qualit…
We propose and characterize experimentally a new source of optical frequency combs for performing multi-heterodyne spectrometry. This comb modality is based on a frequency shifting loop seeded with a CW monochromatic laser. The comb lines are generated by successive passes of the CW laser through an acousto-optic frequency shifter. We report the generation of frequency combs with more than 1500 mutually coherent lines, without resorting to non-linear broadening phenomena or external electronic modulation. The comb line spacing is easily reconfigurable from tens of MHz down to the kHz region. W…
Many optical systems use acousto-optics for fast steering of light. However, acousto-optic (AO) light diffraction permits manipulation and shaping of light fields in a much broader sense including holography. While acousto-optic devices operate at incontestable speed, they are one dimensional (1D) diffraction devices depending on analog serial data transfer and as such have a mode of use distinguished from common 2D spatial light modulators. Combination with an amplified laser source allows to clock the serial buildup of AO diffraction patterns for avoidance of phase aberration in the output b…
The stabilization of lasers to absolute frequency references is a fundamental requirement in several areas of atomic, molecular and optical physics. A range of techniques are available to produce a suitable reference onto which one can 'lock' the laser, many of which depend on the specific internal structure of the reference or are sensitive to laser intensity noise. We present a novel method using the frequency modulation of an acousto-optic modulator's carrier (drive) signal to generate two spatially separated beams, with a frequency difference of only a few MHz. These beams are used to prob…
We consider the acousto-optic effect in a random medium. We derive the radiative transport equations that describe the propagation of multiply-scattered light in a medium whose dielectric permittivity is modulated by an acoustic wave. Using this result, we present an analysis of the sensitivity of an acousto-optic measurement to the presence of a small absorbing inhomogeneity.
We propose a strategy for quantitative photoacoustic mapping of chromophore concentrations that can be performed purely experimentally. We exploit the possibility of acousto-optic modulation using focused ultrasound, and the principle that photons follow trajectories through a turbid medium in two directions with equal probability. A theory is presented that expresses the local absorption coefficient inside a medium in terms of noninvasively measured quantities and experimental parameters. Proof of the validity of the theory is given with Monte Carlo simulations.
Acousto-optical devices, such as modulators, filters or deflectors, implement a simple and effective way of light modulation and signal processing techniques. However, their operation wavelengths are restricted to visible and near-infrared frequency region due to a quadratic decrease of the efficiency of acousto-optical interaction with the wavelength increase. At the same time, almost all materials with high value of acousto-optic figure of merit are non-transparent at wavelengths larger than 5 μm, while the transparent materials possess significantly lower acousto-optic figure of merit. Here…
Emerging technologies based on tailorable interactions between photons and phonons promise new capabilities ranging from high-fidelity microwave signal processing to non-reciprocal optics and quantum state control. While such light-sound couplings have been studied in a variety of physical systems, many implementations rely on non-standard materials and fabrication schemes that are challenging to co-implement with standard integrated photonic circuitry. Notably, despite significant advances in integrated electro-optic modulators, related acousto-optic modulator concepts have remained relativel…
We propose theory for reversible quantum transducer connecting superconducting qubits and optical photons using acoustic waves in piezoelectrics. The proposed device consists of integrated acousto-optic resonator that utilizes stimulated Brillouin scattering for phonon-photon conversion, and piezoelectric effect for coupling of phonons to qubits. We evaluate the phonon-photon coupling rate, and show that the required power of optical pump as well as the other device parameters providing full and faithful quantum conversion are feasible for implementation with the state of the art integrated ac…
Frequency modulation of a continuous wave laser source enables generation of photons at multiple frequencies from a single pump laser. Such multiple closely spaced laser lines are important for high data rate QAM in dense-WDM networks. In this paper we present a monolithic silicon acousto-optic frequency modulator (AOFM) operating at 1.09GHz. We demonstrate frequency modulation of a 1564nm wavelength pump laser, resulting in generation of sideband laser lines spaced by 0.009nm.
Acousto-optic devices utilize the overlap of acoustic and optical fields to facilitate photon-phonon interactions. For tightly confined optical and acoustic fields, such as the sub-wavelength scales achievable in integrated devices, this interaction is enhanced. Broadband operation which fully benefits from this enhancement requires light and sound to co-propagate in the same cross-section, a geometry currently lacking in the field. We introduce the `acoustic-optical multiplexer', which enables this co-linear geometry, and demonstrate through simulations a proof-of-concept design. Using suspen…
Acousto-optic interactions involving propagating phonons can break the time-reversal and frequency-modulation symmetry of light. However, conventional acousto-optic modulators based on bulk materials have frequency bandwidth limited to hundreds of megahertz due to their large structural sizes. Here, we experimentally demonstrate gigahertz single-sideband acousto-optic modulation on an etchless lithium niobate integrated platform by using photonic bound states in the continuum. The upper- or lower-sideband modulation of light can be obtained conveniently by choosing specific combinations of inp…
Studying the internal structure of complex samples with light is an important task, but a difficult challenge due to light scattering. While the complex optical distortions induced by multiple scattering can be effectively undone with the knowledge of the medium's scattering-matrix, this matrix is generally unknown, and cannot be measured with high resolution without the presence of fluorescent or absorbing probes at all points of interest. To overcome these limitations, we introduce here the concept of the acousto-optic transmission matrix (AOTM). Taking advantage of the near scattering-free …
Acousto-optic tomography (AOT) enables optical-contrast imaging deep inside scattering samples via localized ultrasound modulation of scattered light. However, the resolution of AOT is inherently limited by the ultrasound focus size, prohibiting microscopic investigations. In the last few years, advances in the field of digital wavefront-shaping have allowed the development of novel approaches for overcoming the acoustic resolution limit of AOT. However, these novel approaches require the execution of thousands of wavefront measurements within the sample speckle decorrelation time, limiting th…
Non-reciprocal components are essential in photonic systems for protecting light sources and for signal routing functions. Acousto-optic methods to produce non-reciprocal devices offer a foundry-compatible alternative to magneto-optic solutions and are especially important for photonic integration. In this paper, we experimentally demonstrate a dynamically reconfigurable non-reciprocal acousto-optic modulator at telecom wavelength. The modulator can be arranged in a multitude of reciprocal and non-reciprocal configurations by means of an external RF input. The dynamic reconfigurability of the …
We report on the implementation of an optical tweezer system for controlled transport of ultracold atoms along a narrow, static confinement channel. The tweezer system is based on high-efficiency acousto-optical deflectors and offers two-dimensional control over beam position. This opens up the possibility for tracking the transport channel when shuttling atomic clouds along the guide, forestalling atom spilling. Multiple clouds can be tracked independently by time-shared tweezer beams addressing individual sites in the channel. The deflectors are controlled using a multichannel direct digital…
We report the design and characterization of high frequency, resonant acousto-optic modulators (AOM) in a MEMS foundry process. The doubly-resonant cavity design, with short ($L{\sim}10.5\, μm$) acoustic and optical cavity lengths, allows us to measure acousto-optic modulation at GHz frequencies with high modulation efficiency. In contrast to traditional AOMs, these devices rely on the perturbation induced by the displacement of cavity boundaries, which can be significantly enhanced in a suspended geometry. This platform can serve as the building block for fast 2D spatial light modulators (SLM…
We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4 ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of $1.7 \times 10^5/\sqrt{\rm Hz}$. Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of $10\,\rm nm/\sqrt{\rm Hz}$. The compact, all-optical design ensures alignment-fre…
Diffuse Optical Tomography (DOT) is a reliable and widespread technique for monitoring qualitative changes in absorption inside highly scattering media. It has been shown, however, that Acousto-Optic (AO) imaging can provide significantly more qualitative information, without the need for inversion algorithms, due to the spatial resolution afforded by ultrasound probing. In this article, we show how, by using multiple-wavelength AO imaging, it is also possible to perform quantitative measurements of absorber concentration inside scattering media.
A highly efficient on-chip acousto-optic modulator, as a key component, occupies an exceptional position in microwave-to-optical conversion. Homogeneous thin-film lithium niobate is preferentially employed to build the suspended configuration forming the acoustic resonant cavity to improve the modulation efficiency of the device. However, the limited cavity length and complex fabrication recipe of the suspended prototype restrain further breakthrough in the modulation efficiency and impose challenges for waveguide fabrication. In this work, based on a nonsuspended thin-film lithium niobate-cha…
High-speed spatial light modulators (SLM) are crucial components for free-space communication and structured illumination imaging. Current approaches for dynamical spatial mode generation, such as liquid crystal SLMs or digital micromirror devices, are limited to a maximum pattern refresh rate of 10 kHz and have a low damage threshold. We demonstrate that arbitrary spatial profiles in a laser pulse can be generated by mapping the temporal radio-frequency (RF) waveform sent to an acousto-optic modulator (AOM) onto the optical field. We find that the fidelity of the SLM performance can be improv…
Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic mod…
The resonant acousto-optic effect is studied both analytically and numerically in the terahertz range where the transverse-optical (TO) phonons play the role of a mediator which strongly couples the ultrasound and light fields. A propagating acoustic wave interacts with the TO phonons via anharmonic channels and opens band gaps in the TO-phonon polariton energy dispersion that results in pronounced Bragg scattering and reflection of the incoming light. The separation in frequency of different Bragg replicas, which is at the heart of acousto-optics, allows us to study the resonant acousto-optic…
We report on a scheme to improve the pointing stability of the first order beam diffracted by an acousto-optic modulator (AOM). Due to thermal effects inside the crystal, the angular position of the beam can change by as much as 1 mrad when the radio-frequency power in the AOM is reduced to decrease the first order beam intensity. This is done for example to perform forced evaporative cooling in ultracold atom experiments using far-off-resonant optical traps. We solve this problem by driving the AOM with two radio-frequencies $f_1$ and $f_2$. The power of $f_2$ is adjusted relative to the powe…
The model of nonlinear interaction of proper waves of photonic crystal with plane acoustic wave was developed. The formulation of the model is reduced to the eigenvalue problem, which can be solved by computer simulations. By means of the formulae given in present paper one can predict which polarizations of acoustic wave can result in Bragg diffraction of optical waves of TE or TM polarizations. Computer simulation allows obtaining amplitudes of interaction waves in the case of Bragg diffraction when phase-matching conditions are fulfilled.
We demonstrate femtosecond pump-probe transient absorption spectroscopy using a programmable dispersive filter as an ultra-fast delay line. Combined with fast synchronous detection this delay line allows for recording of 6 ps decay traces at 34 kHz. With such acquisition speed we perform single point pump-probe spectroscopy on bulk samples in 80 $μ$s and hyperspectral pump-probe imaging over a field of view of 100 $μ$m in less than a second. The usability of the method is illustrated on a showcase experiment to image and discriminate two pigments in a mixture.
Push-Pull acousto-optic modulator based on non-suspended thin-film lithium niobate on silicon substrate
Elmore Family School of Electrical and Computer Engineering, Purdue University（普渡大学埃尔莫电气与计算机工程学院）；Department of Electrical and Computer Engineering, University of Michigan（密歇根大学电气与计算机工程系）
A theoretical study on the stimulated Brillouin scattering (SBS) in a sub-wavelength anisotropic waveguide is conducted. The optical, photoelastic and mechanical anisotropies of the waveguide materials are all taken into account. First, the integral formulae for calculating the acousto-optical coupling coefficients (AOCCs) due to the photoelastic and moving interface effects in SBS are extended to an optically anisotropic waveguide. Then, with the extended formulae, the SBSs in an elliptical nanowire with strong transverse anisotropies are simulated. In the simulations, the elastic fields are …
