yu chieh Cheng

• MS
• Professor (Assistant) at National Taipei University of Technology

For a diffractive waveguide-based augmented reality display, we demonstrate a rapid and straightforward method to define the most compact layout of an exit pupil expander (EPE) from an analysis of diffractive optical elements in kspace. The idea is to consider all k-vectors coming from in-coupling to out-coupling areas according to the grating theo...

We propose a translationally invariant metamirror for light filtering in reflection. The device consists of a thin transverse grating in the micron scale positioned in front of a flat mirror. We analyze the performance of such a photonic metamirror and find a modification of the angular spectrum of the reflected beams, leading to a significant redu...

Kirigami, a technique that transforms 2D sheets into complex designable 3D sculptures, is often used in paper art. In article number 1906233, Yu‐Chieh Cheng, Hao Zeng, and co‐workers implement kirigami in light‐responsive thin‐film liquid‐crystal network actuators. A versatile 3D shape‐shifting and multigait rolling robot capable of light‐steered 2...

The development of stimuli-responsive soft actuators, a task largely undertaken by material scientists, has become a major driving force in pushing the frontiers of microrobotics. Devices made of soft active materials are often-times small in size, remotely and wirelessly powered/controlled, and capable of adapting themselves to unexpected hurdles....

We have been numerically demonstrated the mechanism of spatial beam filtering with autocloned photonic crystals. The spatial filtering through different configurations of the multilayered structures based on a harmonically modulated substrate profile is considered. The paper demonstrates a series of parameter studies to look for the best spatial be...

Refractive index sensors based on surface plasmon resonance (SPR) promise to deliver high sensitivities. However, these sensitivities depend on the derivative of the monitored SPR parameters near resonance, so this dependency leads to a relatively narrow detection range for refractive index changes. Herein, we introduce an idea to improve the detec...

This article reviews recent progress towards the design of near-field flat focusing mirrors, focusing/imaging light patterns in reflection. An important feature of such flat focusing mirrors is their transverse invariance, as they do not possess any optical axis. We start with a review of the physical background to the different focusing mechanisms...

Flat focusing mirrors without any optical axis have been investigated by metallic nanoantennas on top of a plasmonic waveguide. The principle of flat focusing mirror is similar to Veselago flat lens, which allows the beam focusing in the near field. The key idea is to provide anomalous lateral displacement that can restrain a beam spreading and eve...

In this study, a smart material that driven by light is demonstrated experimentally. We doped some liquid crystal monomer in soft polymer to make them being controllable by light illumination. By using this method, the polymer we made behave like bending, stretching, etc.

This proposed research plan aims at developing a new generation of intelligent microrobot by using optically responsive smart elastomers. This kind of light-driven smart material, named liquid crystal elastomer (LCE), can realize microrobots with bio-inspired functionalities, at the same time bring novel alternatives in photonic devising and tunabl...

We present the flat focusing mirror - the dielectric mirrors capable to focus and image the narrow beams in reflections. The mirrors are flat, and transversally invariant, i.e. have no optical axis. We consider two different configurations of such mirrors: 1) Bragg-like mirrors, consisting of structure of specially designed dielectric layers; 2) pe...

Recently, the principle of flat focusing based on one-dimensionally chirped dielectric mirrors has been proposed and experimentally demonstrated. The flat chirped mirror causes anomalous diffraction of the beam during reflection, opposite to the normal diffraction in free space propagation. The anomalous diffraction compensates the normal diffracti...

An approach to switching between different patterns of light beams transmitted through the woodpile photonic crystals filled with liquid crystals is proposed. The phase transition between the nematic and isotropic liquid crystal states leads to an observable variation of the spatial pattern transmitted through the photonic structure. The transmissi...

We propose a periodic structure that behaves as a fluid–fluid composite for sound waves, where the building blocks are clusters of rigid scatterers. Such building-blocks are penetrable for acoustic waves, and their properties can be tuned by selecting the filling fraction. The equivalence with a fluid–fluid system of such a doubly periodic composit...

We experimentally demonstrate the recently predicted effect of near-field focusing for light beams from flat dielectric subwavelength gratings (SWGs). This SWGs were designed for visible light 532 nm and fabricated by direct laser writing in a negative photoresist, with the refractive index and the period . The laterally invariant gratings can focu...

The control of spatial propagation properties of narrow light beams such as divergence, focusing or imaging are main objectives in optics and photonics. In this letter, we propose and demonstrate experimentally a flat focusing mirror, based on an especially designed dielectric structure without any optical axis. More generally, it also enables imag...

A negative Goos-Hänchen (GH) shift of light beam reflecting from planar microphotonic structures consisting of two parallel dielectric subwavelength diffraction gratings is predicted. The phenomenon occurs because the energy flow of the mode guided in the subwavelength structure is predominantly directed in the opposite direction to the energy flow...

Recently the beam focusing in reflection from chirped dielectric mirror has been proposed and demonstrated, where the negative (anomalous) diffraction is responsible for this flat mirror focusing. For a strong focusing performance (large focal distance), a wide angular range of strong (negative) angular dispersion is required. We show that a defect...

A novel application of chirped dielectric mirrors for narrow beam focalization is proposed and demonstrated numerically and experimentally. Analogy to temporal dispersion compensation by chirped dielectric mirrors is discussed.

We predict that narrow beams, reflecting from flat subwavelength diffraction gratings, can focus. The effect is shown for the beams of electromagnetic radiation; however, it should be observable for beams of waves of arbitrary nature (microwaves, surface plasmons, and acoustic and mechanical waves). We present analytical estimations of the focusing...

In this study, the photonic crystal cavity has been designed, fabricated, and characterized in GaN bulk materials with the double heterostructure, which can provide high Q-factor. The cavity is characterized by optical pumping. The resonant mode is observed at the wavelength of 362 nm. The threshold of excitation power is found to be 0.9 mW, corres...

A novel use of chirped mirrors for narrow beam focalization is proposed. Focusing in reflection from flat chirped mirror has been demonstrated numerically and experimentally. Analogy to temporal dispersion mirrors is discussed.

Unlocked evanescent waves in periodic medium are characterized by Bloch modes which wave vector has real part in between the Brillouin zone and non zero imaginary part. Because of these properties, we report here the relevance of the k-space of unlocked evanescent waves in thin semi-infinite fluid-fluid sonic crystal slabs.

We predict the existence of evanescent modes with unlocked phases in two-dimensional (2D) dielectric periodic structures. Contrary to what is known for one-dimensional structures, where evanescent fields lock to the host modulation, we show that in 2D systems a new class of evanescent modes exists with an unlocked real part of the wave vector. Henc...

Photonic crystals (PhCs) attracted a great amount of attention because of their capability to control the light propagation, in particular due to photonic band-gaps for plane waves in frequency domain. Spatial propagation of beams has been also considered in PhCs bringing to realization, among others, a negative refraction and consequently, allowin...

We propose and demonstrate a novel functionality of chirped mirror for monochromatic light beams: a diffraction control in reflections resulting in focusing or imaging of beams. The chirped mirrors, commonly used for manipulating temporal profiles of pulses, here are applied for manipulating the spatial dispersion of a monochromatic beam. By penetr...

We propose and show by proof-of-principle calculations and experiments that beam focusing and imaging can be obtained in reflection from a flat interface of a micromodulated dielectric structure. We show, in particular, that a one-dimensionally modulated and chirped structure can focus a beam, performing an imaging of a light pattern, i.e., can act...

We predict and show the existence of unlocked evanescent waves in two dimensional periodic structures. In a one dimensional periodic structure an evanescent mode are located either at the center or at the boundary of the Brillouin Zone, and the real part of wave-vectors is locked either to zero or to the modulation vector of the periodicity. Howeve...

form only given. We explore reflections of narrow beams from one-dimensionally modulated photonic structures, where the modulation period varies across the structure (the so called chirped dielectric mirrors). It is known, that the plane waves reflected in a normal direction from the chirped mirrors, can show modified temporal dispersion [1]. Diffe...