Interrogating an object with a light beam and analyzing the scattered light can reveal kinematic information about the object, which is vital for applications ranging from autonomous vehicles to gesture recognition and virtual reality. We show that by analyzing the change in the orbital angular momentum (OAM) of a tilted light beam eclipsed by a moving object, lateral motion of the object can be detected in an arbitrary direction using a single light beam and without object image reconstruction. We observe OAM spectral asymmetry that corresponds to the lateral motion direction along an arbitrary axis perpendicular to the plane containing the light beam and OAM measurement axes. These findings extend OAM-based remote sensing to detection of non-rotational qualities of objects and may also have extensions to other electromagnetic wave regimes, including radio and sound.

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Detecting Lateral Motion using Light's Orbital Angular Momentum.

In this paper, we used the novel defective resonant cavities to design an eight-channel photonic crystal demultiplexer. We showed that by choosing appropriate values for the width of the resonant cavity, the desired wavelengths can be separated. The proposed platform has a square lattice of dielectric rods immersed in air. The value of transmission efficiency for channels was obtained in 94$$-$$-99 % range. In addition, the maximum value of crosstalk and average quality factor for channels were calculated ---11.2 dB and 2200, respectively.

A new proposal for eight-channel optical demultiplexer based on photonic crystal resonant cavities

We theoretically analyze the detection of a cancer cell in the one-dimensional photonic crystal by infiltrating different sample cells in the cavity layer. The defect modes appear in their transmission spectra only if the nanocomposite layers are included on either side of the cavity layer. This analysis is carried out by a dielectric constant and the transmittance peak of the cancer cell is compared with the normal cell. The transmittance peak shifts are analyzed with various filling factors for optimization purposes. Through the shifting spectrum, the sensitivity of cancer cell from the normal cell is obtained from a minimum of 42 nm/RIU to a maximum of 43 nm/RIU.

Enhanced sensitivity of cancer cell using one dimensional nano composite material coated photonic crystal

Light beams can be characterized by their complex spatial profiles in both intensity and phase. Analogous to time signals, which can be decomposed into multiple orthogonal frequency functions, a light beam can also be decomposed into a set of spatial modes that are taken from an orthogonal basis. Such decomposition can potentially provide a tool for spatial spectrum analysis, which may enable stable, accurate, and robust extraction of physical object information that may not be readily achievable using traditional approaches. As a proof-of-concept example, we measure an object’s opening angle using orbital-angular-momentum (OAM) -based complex spectrum, achieving a >15  dB signal-to-noise ratio. Moreover, the dip (i.e., notch) positions of the OAM intensity spectrum are dependent on an object’s opening angle but independent of the opening’s angular orientation, whereas the slope of the OAM phase spectrum is dependent on the opening’s orientation but independent of the opening angle.

Using a complex optical orbital-angular-momentum spectrum to measure object parameters.

Light beams can be characterized by their complex spatial profiles in both intensity and phase Analogous to time signals, which can be decomposed into multiple orthogonal frequency functions, a light beam can also be decomposed into a set of spatial modes that are taken from an orthogonal basis Such a decomposition can provide a tool for spatial spectrum analysis, which may allow the stable, accurate and robust extraction of physical object information that may not be readily achievable using traditional approaches As an example, we measure the opening angle of an object using the complex spectrum of orbital angular momentum (OAM) modes as the basis, achieving a more than 15 dB signal-to-noise ratio We find that the dip (ie, notch) positions of the OAM intensity spectrum are dependent on an object's opening angle but independent of the object opening's angular orientation, whereas the slope of the OAM phase spectrum is dependent on the object opening's orientation but independent on the opening angle

Using a Complex Optical Orbital-Angular-Momentum Spectrum to Measure Object Parameters: A Spatial Domain Approach

All-optical switch based on photonic crystal microcavity with multi-resonant modes

We present a simple method to design one-dimensional (1D) multichannel filters based on the resonant coupling theory, which can choose not only the peak frequency of each channel but also the quality factors (Q values) independently. This method is described by three samples for the design of two-channel, three-channel, and four-channel filters. An additional defect is introduced symmetrically into both sides of the 1D PhCs—it can generate defect modes that overlap with the channels that require tuning. This defect makes the Q values of these channels reduced but with no frequency shift, while the other channels almost keep invariant. The method is valuable for the design of multichannel filters with each channel and bandwidth adjustable independently.

Wenyuan Rao

Papers

All-optical switch based on photonic crystal microcavity with multi-resonant modes

Design of multichannel filters with each channel wavelength and bandwidth adjustable independently