Discrete Mode Laser Diodes with Ultra Narrow Linewidth Emission ≪ 3kHz

Abstract

Ex-facet, free-running ultra-low linewidth (< 3 kHz), single mode laser emission is demonstrated using low cost, regrowth-free ridge waveguide Discrete Mode Fabry Pérot laser diode chips.

Ultra-narrow-linewidth, single-frequency distributed feedback waveguide laser in Al_2O_3:Er^3+ on silicon

“…2(c). The linewidth is narrower than the 2:7 kHz linewidth produced by a discrete-mode laser diode, which was claimed to have been the narrowest linewidth of any free-running monolithic laser [15]. Standard semiconductor DFB lasers typically have linewidths that are a few orders of magnitude larger owing to longitudinal spatial hole burning when carriers are depleted by the nonuniform photon distribution [16].…”

A full‐duplex dual‐polarization QPSK in a digital radio‐over‐fiber system

“…As illustrated in Figure 6, DSP enables the system to perfectly work even for the laser linewidth up to 10 MHz (for a distributed-feedback [DFB] laser, typical linewidth values are in the range of 500 kHz to10 MHz). 29 Comparing the two test harnesses (with/without DSP), the EVM drop provided in Figure 6 is due to the increment in relative intensity noise (RIN) caused by the laser phase noise. 30 It can be seen that the EVM degradation of~2.9 dB is expected for a 1 MHz…”

“…In order to assess the effect of the linewidth of the laser source at λ 1 , for SNR fixed at 12 dB (60 GHz modulated signal to AWGN level), the linewidth of the input laser is varied from 0.2 MHz to 10 MHz while using a 200 km length of fiber. As illustrated in Figure , DSP enables the system to perfectly work even for the laser linewidth up to 10 MHz (for a distributed‐feedback [DFB] laser, typical linewidth values are in the range of 500 kHz to10 MHz) . Comparing the two test harnesses (with/without DSP), the EVM drop provided in Figure is due to the increment in relative intensity noise (RIN) caused by the laser phase noise .…”

“…On the other hand, an optical amplifier is required to provide the sufficient power level for coherent receiver that may cause further noise due to the amplified spontaneous emission noise from the amplifier. Also, the phase noise can be canceled by employing digital phase locked loop in the hardware domain . Using DSP, the phase locking can be replaced by phase estimation in digital domain which results in obtaining more cost‐effective schemes.…”

“…Also, the phase noise can be canceled by employing digital phase locked loop in the hardware domain. 28,29 Using DSP, the phase locking can be replaced by phase estimation in digital domain which results in obtaining more cost-effective schemes. In the DSP module, the fourth power algorithm 30,31 is used to recover and subsequently remove the remaining phase mismatch between the local oscillator and the signal.…”