Narrow Spectral Width FP Lasers for High-Speed Short-Reach Applications

Vertically Coupled Partially Tapered Ridge Waveguide Semiconductor FP Laser With Improved Divergence Angles

“…Through above design optimization, we have obtained a set of structural parameters that can effectively reduce the far-field divergence angles. We will then simulate the device performance by exploiting a direct numerical convolution model [28,29]. Other than those FP laser parameters given in Table I, we have had the rest device parameters summarized in Table II.…”

Suppression of Mode Partition Noise in FP Laser by Frequency Modulation Non-Coherent Detection

“…Other alternative methods have been proposed to reduce the MPN over the past years [16]- [18]. It was demonstrated that the MPN with its dominant components appearing in the low frequency band can be suppressed by the semiconductor optical amplifier acting as a high-pass filter [16].…”

“…Mode-locked lasers by incorporating a saturable absorber and a gain-modulated semiconductor optical amplifier (SOA) along with spectral filtering in an external cavity, were proposed respectively for effective reduction of the MPN [17]. Yet another approach exploited a built-in bandpass filter to narrow the spectral width of the FP laser hence to reduce the MPN [18]. All these approaches, however, either can hardly be justified in terms of their cost; or falls behind in system performance (due to incomplete elimination of the MPN), as compared to the DFB laser solution.…”

“…𝑠 (𝑧, 𝑡) − 𝛼]}• 𝐹(𝑧, 𝑡) + 𝑗𝜅𝑅(𝑧, 𝑡) + 𝑠̃𝑓(𝑧, 𝑡), 𝑠 (𝑧, 𝑡)− 𝛼]}• 𝑅(𝑧, 𝑡) + 𝑗𝜅𝐹(𝑧, 𝑡) + 𝑠̃𝑟(𝑧, 𝑡),(26) where𝑁(𝑧, 𝑡) is the carrier density, 𝐼(𝑡) the injected current, 𝑒 the electron charge, 𝑉 the active region volume, 𝜏 𝑐 the carrier lifetime, 𝑣 𝑔 = 𝑐 𝑛 𝑔 ⁄ the group velocity, 𝑐 the speed of light, 𝑛 𝑔 the group index, 𝑃 𝑠 (𝑧, 𝑡) = 𝑛 𝑒𝑓𝑓 (𝑧, 𝑡)| 2 + |𝑅(𝑧, 𝑡)| 2 ] the photon density distribution, 𝑛 𝑒𝑓𝑓 = 𝑛 𝑒𝑓𝑓 0 − 𝜆 0 (4𝜋) ⁄ 𝛼 𝐿𝐸𝐹 𝛤𝑔(𝑧, 𝑡) effective index, 𝑛 𝑒𝑓𝑓 0 effective index without injection, 𝜆 0 the peak gain wavelength, 𝛼 𝐿𝐸𝐹 linewidth enhancement factor, 𝛤 the optical confinement factor, 𝑔(𝑧, 𝑡) = 𝑎 ln[𝑁(𝑧, 𝑡) 𝑁 0⁄ ] the material optical gain, 𝑎 the material gain coefficient, 𝑁 0 the transparent carrier density, ℎ Planck's constant, 𝑣 0 the optical frequency corresponding to 𝜆 0 , 𝜀 0 the permittivity of a vacuum, 𝜇 0 the permeability of a vacuum, 𝑑 thickness of active region, 𝑤 width of active region, 𝐹(𝑧, 𝑡) the slowly varying envelopes of the forward propagating fields, 𝑅(𝑧, 𝑡) the slowly varying envelopes of the backward propagating fields, 𝜀 nonlinear gain suppression coefficient, 𝑗 the imaginary unit, 𝛿 = [2𝜋𝑛 𝑒𝑓𝑓 0 𝐿𝐸𝐹 𝛤𝑔(𝑧, 𝑡) − 𝜋 Λ ⁄ ] the phase detuning factor from the Bragg wavelength, 𝛬 Bragg grating period, 𝛼 the optical modal loss, and 𝜅 grating coupling coefficient.The magnitude of the spontaneous emission noise fields 𝑠̃𝑓(𝑧, 𝑡) and 𝑠̃𝑟(𝑧, 𝑡) are treated in a similar way as(18) in Appendix A: 〈|𝑠̃𝑓 ,𝑟 (𝑧, 𝑡)||𝑆 ̃𝑓,𝑟 (𝑧 ′ , 𝑡 ′ − 𝑧 ′ )𝛿(𝑡 − 𝑡 ′ ),…”