Periodic structural defects in Bragg gratings and their application in multiwavelength devices

Rulei Xiao; Yuechun Shi; Renjia Guo; Ting Chen; Lijun Hao; Xiangfei Chen

doi:10.1364/prj.4.000035

Journals >Photonics Research >Volume 4 >Issue 2 >Page 0035 > Article

Photonics Research
Vol. 4, Issue 2, 0035 (2016)

Periodic structural defects in Bragg gratings and their application in multiwavelength devices

Rulei Xiao, Yuechun Shi^*, Renjia Guo, Ting Chen, Lijun Hao, and Xiangfei Chen

Author Affiliations

National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China

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DOI: 10.1364/prj.4.000035 Cite this Article Set citation alerts

Rulei Xiao, Yuechun Shi, Renjia Guo, Ting Chen, Lijun Hao, Xiangfei Chen. Periodic structural defects in Bragg gratings and their application in multiwavelength devices[J]. Photonics Research, 2016, 4(2): 0035 Copy Citation Text

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Fig. 1. (a) Schematic and (b) transmission spectra of the uniform Bragg grating with PSDs and without PSDs.

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Fig. 2. 2D transmission spectra when the relative defect size is changed from −0.5 to 0.5.

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Fig. 3. 2D transmission spectra when the period of defects is changed from 1.0 to 10 μm.

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Fig. 4. (a) Bragg wavelengths of 0 and ±1-order subgratings and (b) the RGS of each order subgrating versus the relative defect size.

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Fig. 5. Comparison of the actual fabrication patterns utilized in an eight-wavelength grating array without PSDs and with PSDs.

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Fig. 6. (a) Transmission spectra of the PSD-based eight-wavelength π-phase-shifted Bragg grating array whose parameters are given in Table 2, and (b) the influence of the DSE.

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Fig. 7. RGS versus occupation ratio of the grating-stitched method. A schematic of a sample unit of the stitched grating is shown in the inset.

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Fig. 8. Lasing spectrum, power [inset (I)], and gain [inset (II)] distribution along the cavity of DFB lasers with PSDs and without PSDs.

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Parameter (Symbol)	Value
Waveguide width ( $w$ )	1 μm
Waveguide height ( $h$ )	0.4 μm
Grating depth ( $d$ )	10 nm
Total length ( $L$ )	300 μm
Grating period ( $Λ$ )	238 nm
Filling factor ( $r$ )	0.5
Waveguide refractive index ( $n 2$ )	3.4
Cladding refractive index ( $n 1$ )	3.1
Defect size ( $D$ )	59.5 nm
Period of defects ( $P$ )	4.5 μm

Table 1. Parameters in TMM Calculation

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Period of Defects (μm)	Bragg Wavelength (nm)	Equivalent Grating Period (nm)
7.740	1535.0	239.84
7.252	1535.8	239.97
6.823	1536.6	240.09
6.442	1537.4	240.22
6.102	1538.2	240.34
5.796	1539.0	240.47
5.519	1539.8	240.59
5.268	1540.6	240.72

Table 2. Periods of Defects for Eight-Wavelength π-Phase-Shifted Bragg Grating Array

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Parameter (Symbol)	Value
Cavity length ( $L$ )	400 μm
Grating period without PSDs ( $Λ$ )	241 nm
Grating period with PSDs ( $Λ_{0}$ )	238 nm
Defect size ( $D$ )	59.5 nm
Period of defects ( $P$ )	4.78 μm
Active layer width ( $w$ )	1.5 μm
Active layer thickness ( $d$ )	0.12 μm
Optical confinement factor ( $Γ$ )	0.3
Effective refractive index	3.2
at bias current ( $n_{eff}$ )
Group refractive index ( $n_{g}$ )	3.7
Refractive index modulation ( $Δ n_{0}$ )	0.003
Filling factor ( $r$ )	0.5
Internal loss ( $α$ )	$4 \times 10^{3} m^{- 1}$
Spontaneous emission rate ( $τ^{- 1}$ )	$2.5 \times 10^{10} s^{- 1}$
Bimolecular recombination	$1 \times 10^{- 16} m^{3} s^{- 1}$
coefficient ( $B$ )
Auger recombination coefficient ( $C$ )	$3 \times 10^{- 41} m^{6} s^{- 1}$
Transparent carrier density ( $N_{0}$ )	$1.2 \times 10^{24} m^{- 3}$
Linear gain coefficient ( $a$ )	$2.7 \times 10^{- 20} m^{2}$
Linewidth enhancement factor ( $β_{C}$ )	1.5
Bias current ( $I_{B}$ )	20 mA