ABSTRACT
A new focusing structure is proposed, consisting of periodic array air holes in silicon and based on two-dimensional (2D) photonic crystal (PC) with negative refraction and subwavelength imaging characteristics. The light radiating from a point source can form a subwavelength imaging of which the half-width reaches 0.47λ through a wedge PC. Due to the influence of the aberration and evanescent field, the symmetry plane of the image is inside the structure rather than the boundary. In addition, moving the PC by 2 µm to the left horizontally, the image moves by 3.57 µm and the half-width of each image is less than the half-wavelength in this process.
ABSTRACT
The negative Goos-Hänchen shift (GHS) on a two-dimensional photonic crystal with an effective negative refractive index is investigated by simulation and experiment. The measured refractive index of the fabricated photonic crystal is nearly -0.44. The difference between the Goos-Hänchen shift of the transverse electric wave GTE and that of the transverse magnetic wave GTM (DGHS) in the height direction of a silicon rod is measured at three incident angles. The result shows that DGHS is always smaller than -GTM, thus GTE<0; therefore, the negative GHS does occur on the surface of the photonic crystal with a negative refractive index.
ABSTRACT
A new two-dimensional (2D) photonic crystal (PC) structure with effective refractive index approaching -1, consisting of periodic array air holes in silicon, is proposed. The light radiated from a point source can form an image through a single wedge PC. Numerical results show that the half-width of the image reaches 0.44λ, which is lower than half of the incident wavelength. In addition, the light through the combination of two of the same PCs can also form subwavelength imaging of which the half-width reaches 0.67λ, and the image almost flipped 180° compared with a point source.
ABSTRACT
Although the inverse Doppler effect has been observed experimentally at optical frequencies in photonic crystal with negative effective refractive index, its explanation is based on phenomenological theory rather than a strict theory. Elucidating the physical mechanism underlying the inverse Doppler shift is necessary. In this article, the primary electrical field component in the photonic crystal that leads to negative refraction was extracted, and the phase evolution of the entire process when light travels through a moving photonic crystal was investigated using static and dynamic finite different time domain methods. The analysis demonstrates the validity of the use of np (the effective refractive index of the photonic crystal in the light path) in these calculations, and reveals the origin of the inverse Doppler effect in photonic crystals.
