Analysis of adiabatic coupling between photonic crystal single-line-defect and coupled-resonator optical waveguides

Abstract

A detailed analysis of adiabatic coupling between conventional photonic crystal single-line-defect and coupled-resonator optical waveguides is reported. Adiabatic coupling by progressive variation of the radii of the spacing defects between cavities is investigated. Flat transmission spectra with coupling efficiencies greater than 90% are achieved in a broad frequency range with short coupling lengths. Moreover, we find that flat transmission at low frequencies requires longer coupling lengths partly because the requirements imposed for adiabatic transmission in photonic crystals are violated.

Experimental results on adiabatic coupling into SOI photonic Crystal coupled-cavity waveguides

“…The improvement occurs at the high wavelengths of the transmission band while sharper resonant peaks appear at the low wavelengths of the band. The latter is originated due to the violation of the condition of adiabaticity occurred for those wavelengths at intermediate points in the taper [5]. However, the wavelength range, in which a rather flat transmission is observed, grows as the taper length increases, as it can be seen in Fig.…”

“…One key issue that needs to be addressed for enabling definitive widespread CCW-based devices is an efficient coupling from an external medium [4]. An adiabatic coupling technique between single-line defect waveguides (SLWGs) and CCWs was recently proposed [5]. Furthermore, the dynamic performance was also investigated by analyzing the transmission of ultrashort pulses through the structure [6].…”

Experimental demonstration of adiabatic coupling into SOI photonic crystal coupled-cavity waveguides

“…However, one key issue that needs to be addressed is an efficient coupling from an external medium. An adiabatic coupling technique between single-line-defect waveguides (SLWGs) and CCWs was recently proposed [2]. Furthermore, their dynamic performance by analyzing the transmission of ultrashort pulses through the structure was also investigated [3].…”

Pulse propagation in adiabatically coupled photonic crystal coupled cavity waveguides

“…However, only a few works have been focused on CCWs. [8][9][10][11][12] An inefficient coupling originates a number of undesired resonance peaks in the transmission spectrum which coincides with the number of cavities that form the CCW. The peak-to-valley ratio of the resonant peaks is mainly determined by the coupling efficiency at the two ends of the CCW.…”

“…The proposed coupling technique is based on varying progressively the radii of the spacing defects between cavities in order to gradually match the SLWG and CCW modes. 11 A rigorous analysis of pulse propagation in both frequency and time domains is carried out in order to analyze the influence of coupling efficiency on the main parameters of the propagated pulse. The obtained results from the proposed adiabatic coupling technique are compared with the case of butt coupling between the SLWGs and the CCW of finite length.…”