Yisa S. Rumala

Tunable supercontinuum light vector vortex beam generator using a q-plate.

Spatially coherent multicolored optical vector vortex beams were created using a tunable liquid crystal q-plate and a supercontinuum light source. The feasibility of the q-plate as a tunable spectral filter (switch) was demonstrated, and the polarization topology of the resulting vector vortex beam was mapped. Potential applications include multiplexing for broadband high-speed optical communication, ultradense data networking, and super-resolution microscopy.

Multiple-beam interference in a spiral phase plate

Optical transmission through a spiral phase plate is analyzed by treating the device as a Fabry–Perot etalon with an azimuthally varying thickness. The transmitted beam is calculated to contain a coherent superposition of optical vortices with different winding numbers. This yields an intensity profile with a periodic modulation as a function of azimuthal angle where the orientation rotates as a function of the laser frequency. These effects are quantified experimentally and theoretically.

Interference theory of multiple optical vortex states in spiral phase plate etalon: thick-plate and thin-plate approximation

The spiral phase plate etalon transmission function is calculated from the low-reflectivity to high-reflectivity regime. Two approximations are considered: thick-plate approximation and thin-plate approximation. The thick-plate approximation explicitly takes into account the angle between the azimuthally increasing surface and the flat surface, while the thin-plate approximation does not. The two results are in agreement in the low-reflectivity regime, but not in the high-reflectivity regime. The thick-plate approximation is expected to provide a more accurate and general description of the device in all regimes. Origins of the device output intensity dependence on angle due to multiple vortex states present in the device are discussed, and a constraint on the number of internal reflections due to device geometry is also discussed.

Propagation of structured light beams after multiple reflections in a spiral phase plate

Abstract. This work presents propagation dynamics of structured light (complex light) containing optical vortices after it has undergone multiple reflections in a spiral phase plate (SPP) device having a nonzero surface reflection. In the calculations, the thick-plate approximation is assumed as it is expected to give a more accurate representation of the standard geometry of an SPP device from a low-surface reflection to a high-surface reflection. Calculations showing the propagation of counter-rotating optical vortices are presented, and the effect of the statistical nature of photons on the observation of the angular intensity modulation of the beam is discussed.

Wave transfer matrix for a spiral phase plate.

The wave transfer matrix (WTM) is applied to calculating various characteristics of a spiral phase plate (SPP) for the first time to our knowledge. This approach provides a more convenient and systematic approach to calculating properties of a multilayered SPP device. In particular, it predicts the optical wave characteristics on the input and output plane of the device when the SPP is fabricated on a substrate of the same refractive index as the SPP as well as on a substrate of a different refractive index compared to the SPP. The dependence of the parameters on the input laser frequency is studied in detail for a low finesse SPP etalon device for both cases. The equations derived from the WTM are used to show that a variation in input laser frequency causes the optical intensity pattern on the output plane to rotate, while preserving the topology of the optical vortex, i.e., the variation in laser frequency has a minimal effect on the parameters describing the azimuthal intensity modulation and orbital angular momentum content of the beam. In addition, the equations predict the presence of longitudinal modes in the SPP device.

Sensitivity in frequency dependent angular rotation of optical vortices.

This paper presents robust strategies to enhance the rotation sensitivity (and resolution) of a coherent superposition of optical vortices emerging from a single spiral phase plate (SPP) device when lights optical frequency (or wavelength) going into the SPP device is varied. The paper discusses the generation and measurement of ultrasmall rotation. Factors that affect the ability to perform precision rotation measurements include the linewidth and stability of the input light source, the number of photon counts making position rotation measurements on the CCD detector, SPP reflectivity, the length of SPP device, and the angular modulation frequency of the intensity pattern due to a coherent superposition of optical vortices in a single SPP device. This paper also discusses parameters to obtain a high-sensitivity single shot measurement and multiple measurements. Furthermore, it presents what I believe is a new scaling showing the enhancement in sensitivity (and resolution) in the standard quantum limit and Heisenberg limit. With experimentally realizable parameters, there is an enhancement of rotation sensitivity by at least one order of magnitude compared to previous rotation measurements with optical vortices. Understanding robust strategies to enhance the rotation sensitivity in an SPP device is important to metrology in general and for building compact SPP sensors such as gyroscopes, molecular sensors, and thermal sensors.

Optical vortex with a small core and Gaussian intensity envelope for light-matter interaction

Optical vortices with a vortex core size that is at least two orders of magnitude smaller than the laser beam waist is presented. The optical vortex is generated by a spiral phase plate (SPP) and counterrotating optical vortex pairs are created in a modified Mach–Zehnder interferometer surrounded by a 4f lens arrangement. The azimuthal variation of the counterrotating optical vortex forms a sinusoidal intensity modulation for which the winding number of the optical vortex is deduced accurately and precisely by fitting it to a sinusoidal function. These results are of interest in designing novel optical vortex gratings for manipulating matter waves (e.g., in Kapitza–Dirac scattering). A theory of atomic angular Kapitza–Dirac scattering with optical vortices is presented. The large beam waist combined with a small optical vortex core size would also be of interest when using an optical vortex to perform spectroscopy in a wide range of matter systems including solid, liquid, atomic, and molecular systems, as well as in short-range optical communication.

Current Applications of Supercontinuum Light

Since the first observation of supercontinuum (SC) light in 1970 by Alfano and Shapiro (1970), numerous applications have emerged. The first application of SC was in inverse Raman scattering (Alfano and Shapiro, 1971) and later for time-resolved laser spectroscopy of liquids and solids. In the previous edition of the book published in 2006, Dorsinville et al. (2006) reviewed many supercontinuum light applications of time resolved absorption spectroscopy (in the areas of solid state physics, chemistry, and biology), time resolved excitation spectroscopy (in the areas of coherent anti-Stokes Raman scattering, and Raman induced Phase conjugation), as well as optical pulse compression. Dorsinville et al. also explored future applications in ranging, imaging, optical computational switches, atmospheric remote sensing, kinetics of nonlinearities in solids, and optical fiber measurements. This chapter does not focus on these previously reviewed topics. Interested readers can refer to the second edition of the book published in 2006.

An analysis of the magic echo and solid echo sequence for quadrupolar echo spectroscopy of spin I = 1 nuclei by average Hamiltonian theory

This work focuses on analyzing the dynamics of spin I = 1 nuclei evolving under a simple two pulse echo cycle and a magic echo cycle by average Hamiltonian theory. The work highlights how spectral artifacts introduced by finite pulse widths can be removed by cycling the phases of the receiver and transmitter in a well defined way. In addition, it is shown that a magic echo cycle can refocus both the quadrupolar interaction together with any offset Hamiltonian. Due to higher convergence in the Magnus expansion magic echo based quadrupolar echo spectroscopy outperforms the conventional two pulse echo sequence.