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A non-Hermitian He-Ne ring laser gyroscope (RLG) that operates at an exceptional point is proposed and experimentally realized. Compared to a standard RLG, the device exhibits more than an order of magnitude enhancement in sensitivity.

Gyroscopes play a crucial role in many and diverse applications associated with navigation, positioning, and inertial sensing [1]. In general, most optical gyroscopes rely on the Sagnac effect -- a relativistically induced phase shift that scales linearly with the rotational velocity [2,3]. In ring laser gyroscopes (RLGs), this shift manifests itself as a resonance splitting in the emission spectrum that can be detected as a beat frequency [4]. The need for ever-more precise RLGs has fueled research activities towards devising new approaches aimed to boost the sensitivity beyond what is dictated by geometrical constraints. In this respect, attempts have been made in the past to use either dispersive or nonlinear effects [5-8]. Here, we experimentally demonstrate an altogether new route based on non-Hermitian singularities or exceptional points in order to enhance the Sagnac scale factor [9-13]. Our results not only can pave the way towards a new generation of ultrasensitive and compact ring laser gyroscopes, but they may also provide practical approaches for developing other classes of integrated sensors., 15 pages

Supersymmetric transformations aim to relate boson and fermions, two different species of particles, and their interactions. In quantum mechanics, the mathematical framework of SUSY can be used to design isospectral potentials. By virtue of the isomorphism between Schrodinger and wave equations, one can use such transformations for designing novel optical systems. In this talk, we review the recent developments in the general area of supersymmetric optics and photonics. We will also discuss the possibility of generating high brightness coherent light in supersymmetric laser arrays.

The synergetic use of gain and loss in parity-time symmetric coupled resonators has been shown to lead to single-mode lasing operation. However, at the corresponding resonance frequency, an ideal ring resonator tends to support two degenerate eigenmodes, traveling along the cavity in opposite directions. Here, we show a unidirectional single-moded parity-time symmetric laser by incorporating active S-bend structures with opposite chirality in the respective ring resonators. Such chiral elements break the rotation symmetry of the ring cavities by providing an asymmetric coupling between the clockwise (CW) and the counterclockwise (CCW) traveling modes, hence creating a new type of exceptional point. This property, consequently, leads to the suppression of one of the counter-propagating modes. In this paper, we first measure the extinction ratio between the CW and CCW modes in a single ring resonator in the presence of an S-bend waveguide. We then experimentally investigate the unidirectional emission in PT-symmetric systems below and above the exceptional point. Finally, unidirectional emission will be shown in systems of two S-bend ring resonators coupled through a link structure.

Multimode emission adversely affects phased-locked laser arrays resulting in chaotic behaviors. Utilizing optical supersymmetry, we experimentally demonstrate a single mode laser array where a superpartner array eliminates undesired higher order transverse modes.