In this paper, two different Passive Mode-Locked Laser Diodes (PMLLD) structures, a Fabry–Perot cavity and a ring cavity laser are characterized and evaluated as monolithic Optical Frequency Comb Generators (OFCG) for CW sub-THz generation. An extensive characterization of the devices under study is carried out based on an automated measurement system that systematically evaluates the dynamic characteristics of the devices, focusing on the figures of merit that define the optimum performance of a pulsed laser source when considered as an OFCG. Sub-THz signals generated with both devices at 60 GHz and 90 GHz are presented and analyzed in terms of electrical linewidth to compare such components for mm-Wave and sub-THz photonic generation. This work offers a systematic comparison of PMLLD devices for OFCG operation and provides reference information of the performance of two different device topologies that can be used for the implementation of photonic integrated sub-THz CW generation.
A prototypical design of AlGaN deep ultraviolet (DUV) laser diodes (LDs) on AlN substrates employing tapered electron blocking layer is presented. Two-dimensional optoelectronic simulation predicts lasing at a target wavelength of 250 nm. Degradation of optical gain associated with spatial separation of electron and hole wave functions inside the active region may be considerably reduced in designs featuring quaternary AlInGaN barriers, by virtue of polarization charge matching. A systematic method for selection of polarization-free quaternary barrier compositions is proposed for 250 nm DUV LD designs, accompanied by a sensitivity analysis. The selection procedure presented here is readily applied to LDs and light-emitting diodes operating at other wavelengths.
Beat-note power spectral density (PSD) of a dispersive semiconductor laser field in the delayed self-heterodyne test is derived by combining the effect of fiber's chromatic dispersion with differential time delay, taking laser's intensity noise (IN) into account, and assuming standard single-mode fiber (SSMF) as an optical channel. This generalized PSD, as it is proven, has asymmetric spectrum due to the high correlation between the dispersive phase noise and the induced IN that is introduced due to channel response. This paper expands our knowledge of the interaction between laser fields with optical channel as well as improving penalty analyses in pilot-aided multicarrier systems such as optical OFDM.
By adjusting an infrared laser power illuminated onto a vanadium dioxide (VO
Modulation instability (MI) in passively mode-locked dissipative solitons lasers has been studied. The factors that affect MI, including the intensity of the nonlinear wave and the linear phase delay of the cavity, have been experimentally studied. It's found that MI induces sidebands in the spectrum of dissipative solitons. The sidebands can cause the pedestal on the pulse in time domain and thus limit the pulse duration. Additionally, a simple method to eliminate the sidebands is proposed and nearly pedestal free pulses are generated correspondingly. Finally, based on MI, a method to measure the cavity net dispersion is proposed and applied to two dissipative soliton lasers with different net dispersion. It's shown that the positions of the adjacent spectral sidebands can determine the intracavity net dispersion, and the measurement error is limited by the accuracy of the optical spectrum analyzer. This indicates it is a simple and precise method to measure the intracavity net dispersion.
Compact, high average output power with picosecond pulses laser was achieved through a carbon nanotube based master oscillator power amplifier, MOPA, configuration. The master oscillator was a single-walled carbon nanotube based passively mode-locked Nd:YVO
A pilot-carrier coherent low-earth-orbit (LEO) satellite to ground (LEO-to-Ground) downlink system using an optical injection phase lock loop (OIPLL) technique is proposed and its feasibility under Doppler frequency shift conditions is demonstrated. A fiber-optic based experimental system is configured and it is demonstrated that a 10 Gbps BPSK transmission system based on the proposed configuration can successfully maintain stable frequency and phase locking status under simulated Doppler frequency shift conditions. It is demonstrated that the stable locking status is maintained over a 10.3 GHz (54
In this paper, the influence of packaging-induced RF signal degradation on an optoelectronic modulator module is investigated. A directly modulated laser (DML) is modeled and packaged in a butterfly-type package. A distributed 3-D electromagnetic model is built based on this laser module. In the packaging assembly procedure, impedance mismatching and ground discontinuity on microwave transmission will cause unwanted signal decays and resonances. We specify the RF degradation in three regions: 1) the RF connector, 2) the RF substrate, and 3) the mode transition region between the optoelectronic subsystem and the package. The RF transmission characteristics in these regions are extracted and analyzed in detail. The results indicate that by optimizing the packaging design, strong resonances and signal decays can be eliminated or compensated over a wide frequency range. The measured scattering parameters show that the proposed packaging assembly has a resonance-free bandwidth of 31.2 GHz, and the DML module exhibits a wide 3 dB bandwidth of 15.1 GHz.
In the absence of optical isolation, semiconductor lasers (SLs) are susceptible to external perturbations that determine the dynamical properties of the generated signals. Mutually coupled SL systems have been proved to exhibit diverse dynamics with the potential to behave synchronously. In this study, a multinodal star all-optical network topology is investigated in terms of synchronization and robustness; 50 SLs with varied operating frequencies around a central frequency
We report an Er-doped, actively Q-switched, fiber laser, generating transform-limited pulses based on single-frequency fiber laser seeded ring cavity. The output pulsewidth can be tuned from hundreds of nanoseconds to several microseconds by changing the repetition rate or the open time of the electrical pulse trigger. This injection-seeded, Q-switched ring cavity fiber laser can be operated over the whole C-band. In addition, a theoretical model is developed to numerically study the pulse characteristics by changing the acousto-optic modulator transmission as well as several cavity parameters, such as the cavity length and loss. The numerical results are in good agreement with the experimental results.