Influence of elliptical shaped holes on the sensitivity and Q factor in 2D photonic crystals sensor

• These structures may not need very stringent fabrication control, unlike the structures employing phase slips or fractional edge dislocations, to achieve the high-Q values.
• The interesting feature in these structures is the role of the ellipses. These are optimized to maximize the Q factor and the sensitivity with high transmission.
• High Q factor and sensitivity are obtained by carefully tuning some structural parameters such as the shape, position and number of the holes surrounding a L2 cavity.

We theoretically investigate the refractive index sensor based on L2 photonic crystal cavity where neighboring holes are locally infiltrated with polymers. The photonic crystal is composed of periodic triangular hole array patterned perpendicularly to an InP-based confining heterostructure. The number of the holes surrounding a L2 cavity and their shape were modified in order to optimize the sensitivity and quality factor. From this study we have selected two structures that have good results. The first one is called locally which has a very high Q factor and a good sensitivity. Their values are 6.03 × 106 and 163 nm/RIU, respectively. The second optimized structure is called design B, which has a high sensitivity toward 227.78 nm/RIU with a Q factor of 5 × 105. The calculated detect limit for the two designs are lower than 1.59 × 10−6 and 1.4 × 10−5 RIU, respectively.