Lib, O. & Bromberg, Y. Spatially entangled Airy photons. Opt. Lett. 45, 6, 1399–1402 (2020). Publisher's VersionAbstract
Over the past decade, Airy beams have been the subject of extensive research, leading to new physical insights and various applications. In this Letter, we extend the concept of Airy beams to the quantum domain. We generate entangled photons in a superposition of two-photon Airy states via spontaneous parametric down conversion, pumped by a classical Airy beam. We show that the entangled Airy photons preserve the intriguing properties of classical Airy beams, such as free acceleration and reduced diffraction, while exhibiting non-classical anti-correlations. Finally, we discuss the advantages offered by entangled Airy photons for high-dimensional free-space quantum communications.
Resisi, S., Viernik, Y., Popoff, S.M. & Bromberg, Y. Wavefront shaping in multimode fibers by transmission matrix engineering. APL Photonics 5, 3, 036103 (2020). Publisher's Version
Bender, N., Yılmaz, H., Bromberg, Y. & Cao, H. Creating and controlling complex light. APL Photonics 4, 11, 110806 (2019). Publisher's Version
Lib, O., Hasson, G. & Bromberg, Y. Real-time shaping of entangled photons by classical control and feedback. arXiv 1902.06653 (2019). Publisher's VersionAbstract

Quantum technologies hold great promise for revolutionizing photonic applications such as cryptography, sensing and imaging. Yet their implementation in real-world scenarios is still held back, mostly due to the sensitivity of quantum states of light to scattering. The recent developments in shaping of single photons introduce new ways to control scattering of quantum light. Here we cancel scattering of entangled photons, by shaping the classical laser beam that stimulates their creation, rather than shaping them directly. We show that when the laser beam and the entangled photons pass through the same diffuser, focusing the laser using classical wavefront shaping recovers the unique correlations of entangled-photons that were scrambled by scattering. Since the shaping process is done exclusively on the classical laser beam, it does not introduce any loss to the entangled photons, and it is not limited by the low signal-to-noise ratios associated with quantum light, opening the door for efficient real-time wavefront shaping for photonic quantum applications.

Bender, N., Yilmaz, H., Bromberg, Y. & Cao, H. Introducing non-local correlations into laser speckles. Opt. Exp. 27, 5, 6057-6067 (2019).
Bromberg, Y., et al. Remote key establishment by random mode mixing in multimode fibers and optical reciprocity. Optical Engineering 58, 1, 016105 (2019).
Xiong, W., et al. Complete polarization control in multimode fibers with polarization and mode coupling. Light: Science & Applications 7, 1, 54 (2018).
Bender, N., Yilmaz, H., Bromberg, Y. & Cao, H. Customizing speckle intensity statistics. Optica 5, 5, 595–600 (2018).Abstract

Speckles commonly satisfy Rayleigh statistics. However, in many applications, non-Rayleigh speckles with customized intensity statistics are desirable. Here, we present a general method for customizing the intensity statistics of speckle patterns on a target plane. By judiciously modulating the phase front of a monochromatic laser beam, we experimentally generate speckle patterns with arbitrarily tailored intensity probability density functions. Relative to Rayleigh speckles, our customized speckles exhibit radically different topologies yet maintain the same spatial correlation length. The customized speckles are fully developed, ergodic, and stationary&\#x2013;with circular non-Gaussian statistics for the complex field. Propagating away from the target plane, the customized speckles revert back to Rayleigh speckles. This work provides a versatile framework for tailoring speckle patterns with varied applications in microscopy, imaging, and optical manipulation.

Ambichl, P., et al. Super- and Anti-Principal-Modes in Multimode Waveguides. Phys. Rev. X 7, 041053 (2017).
Xiong, W., et al. Principal modes in multimode fibers: exploring the crossover from weak to strong mode coupling. Opt. Express 25, 2709–2724 (2017).Abstract

We present experimental and numerical studies on principal modes in a multimode fiber with mode coupling. By applying external stress to the fiber and gradually adjusting the stress, we have realized a transition from weak to strong mode coupling, which corresponds to the transition from single scattering to multiple scattering in mode space. Our experiments show that principal modes have distinct spatial and spectral characteristic in the weak and strong mode coupling regimes. We also investigate the bandwidth of the principal modes, in particular, the dependence of the bandwidth on the delay time, and the effects of the mode-dependent loss. By analyzing the path-length distributions, we discover two distinct mechanisms that are responsible for the bandwidth of principal modes in weak and strong mode coupling regimes. Their interplay leads to a non-monotonic transition of the average principal mode bandwidth from weak to strong mode coupling. Taking into account the mode-dependent loss in the fiber, our numerical results are in qualitative agreement with our experimental observations. Our study paves the way for exploring potential applications of principal modes in communication, imaging and spectroscopy.

Sarma, R., Yamilov, A.G., Petrenko, S., Bromberg, Y. & Cao, H. Control of Energy Density inside a Disordered Medium by Coupling to Open or Closed Channels. Phys. Rev. Lett. 117, 086803 (2016).
Redding, B., Liew, S.F., Bromberg, Y., Sarma, R. & Cao, H. Evanescently coupled multimode spiral spectrometer. Optica 3, 956–962 (2016).Abstract

We designed a high-resolution compact spectrometer based on an evanescently coupled multimode spiral waveguide. Interference between the modes in the waveguide forms a wavelength-dependent speckle pattern, which is used as a fingerprint to identify the input wavelength after calibration. Evanescent coupling between neighboring arms of the spiral results in a non-resonant broadband enhancement of the spectral resolution. Experimentally, we demonstrated a resolution of 0.01 nm at a wavelength of 1520 nm using a 250 &\#x03BC;m radius spiral structure. Spectra containing 40 independent spectral channels are recovered simultaneously, and the operation bandwidth is significantly increased by applying compressive sensing to sparse spectra reconstruction. The ability to achieve such high resolution with low loss in a compact footprint is expected to have a significant impact on low-cost portable sensing and to add functionality to lab-on-a-chip systems.

Xiong, W., et al. Spatiotemporal Control of Light Transmission through a Multimode Fiber with Strong Mode Coupling. Phys. Rev. Lett. 117, 053901 (2016).
Bromberg, Y., Redding, B., Popoff, S.M. & Cao, H. Control of coherent backscattering by breaking optical reciprocity. Phys. Rev. A 93, 023826 (2016).
Reimer, C., et al. Generation of multiphoton entangled quantum states by means of integrated frequency combs. Science 351, 1176–1180 (2016).
Hsu, C.W., Goetschy, A., Bromberg, Y., Stone, D.A. & Cao, H. Broadband Coherent Enhancement of Transmission and Absorption in Disordered Media. Phys. Rev. Lett. 115, 223901 (2015).
Koirala, M., et al. Critical states embedded in the continuum. New Journal of Physics 17, 013003 (2015).
Redding, B., Bromberg, Y., Choma, M.A. & Cao, H. Full-field interferometric confocal microscopy using a VCSEL array. Optics letters 39, 4446–4449 (2014).
Bromberg, Y. & Cao, H. Generating non-Rayleigh speckles with tailored intensity statistics. Physical Review Letters 112, 213904 (2014).
Basiri, A., Bromberg, Y., Yamilov, A., Cao, H. & Kottos, T. Light localization induced by a random imaginary refractive index. Physical Review A 90, 043815 (2014).