Design and simulation of tapered optical fiber by enhancing the evanescent field region for sensing application

We report the design and simulation of the tapered optical fiber with large presence of the evanescent field. The evanescent field of the optical fiber is strongly affected by the surrounding environment which will be exploited into fabricating variety of photonic-based devices such as photodetectors, optical sensors and ultra-high Q resonators. The simulation results show that by adiabatically tapered the waist region, there is a fairly large amount of evanescent field intensity observed at the air-cladding region. The smooth transition region of the tapered fiber has also minimized the multimode interference in the waist and transition region thus reducing the energy loss and contributing to the higher output power

Photonic crystal embedded waveguide for compact C-band band-pass filter

We report the modelling of a band-pass filter at conventional band (c-band) and the effect of different shapes of photonic crystal (PhC) holes embedded on silicon-on-insulator (SOI) waveguide. The designed embedded waveguides was simulated with LUMERICAL finite different time domain (FDTD) and a filter response with a bandwidth of approximately 30 nm complying with international telecommunication unit (ITU-T) standard was observed. The simulated bandwidth observed was sufficient for guarding against other band interference in telecommunication applications such as wavelength division multiplexing (WDM). The waveguide was designed with a dimension of 600 nm width × 260 nm height and embedded with PhC of 4 mirrors and 3 cavities. 2 mirrors at both end of the whole structure were designed with less number of holes for obtaining the band-pass filter profile. With a value of lattice constant a, hole radius r and cavity distance c of 370, 115 and 315 nm respectively, the simulated device spectrum complimented the erbium doped fiber amplifier (EDFA) spectrum to obtain wavelength profile flatness. The PhC embedded waveguide was tailored to give a 70 percent value of transmission. A flat profile was observed by reducing the photonic crystal hole radii in the middle mirrors. The wavelength band and the bandwidth of the band can be tuned by manipulating the number of mirrors and cavities in waveguide. A different types of PhC hole shapes were also studied and compared. The transmission quality and bandpass quality with different types of hole shapes show that the circular PhC shape are superior in comparison with square hole shapes

Photonic crystal (PhC) nanowires for infrared photodetectors

We report the Photonic Crystal (PhC) nanowires performance for potential phototodetectors integration application. The refractive index of PhC can be tailored to guide specific resonance wavelength precisely. This paper presents the numerical approach of 1D PhC with 12 periodic holes to observe the range of stop band acquired, transmission and the quality factor of the resonance wavelengths. By splitting the holes equally with a range of cavities from 440 to 450 nm, the stop band observed are between 1.5 to 2.1 μm. By varying the cavity length, the value of resonance wavelengths and quality factors observed have also changed. The introduction of 442 nm cavity shows the highest transmission but the lowest Quality factor (Q-factor) where both are observed at 0.87 and 284 respectively. The values indicate a good confinement of light in the waveguide designed thus enabling wavelength selectivity for photodetectors application in highly sensitive wavelength selection application