External optical feedback effects on stability of asymmetric DFB-FL and isolation method

On-chip integration of semiconductor lasers have shown a growing interest in recent years, especially for the development of photonic integrated circuits (PICs) which are of paramount importance for high-speed communication within and between data centers, and fast on-board data exchanges. For all these applications, a key challenge remains the stability of the laser sources integrated on a PIC in presence of external optical feedback with the view to avoid integrated bulky and costly optical isolation. In this study, the effects of external optical feedback are investigated in hybrid InAs/InP quantum dot comb lasers on silicon. The design of the cavity includes a semiconductor optical amplifier section, a saturable absorber and an on-chip external cavity incorporating a vertical coupler. We measured the resulting feedback properties with respect to the operation conditions (bias current and voltage) and to the length of the saturable absorber. We show that under most operating conditions, the laser remains stable against optical feedback, only few regimes of operation occur, which either improve or degrade the frequency comb and/or the radio-frequency beatnote power of the laser.

The effect of external optical feedback on a packaged monolithic quantum dot passively mode-locked laser is investigated. The radio-frequency (RF) linewidth narrows from 8 KHz in the free-running situation to a value as low as 170 Hz under relatively low feedback and temperature control. The RF linewidth characterization under resonant feedback at a multiple of the laser cavity length agrees well with the published theory. The narrow RF linewidth with external optical feedback makes the chip-scale quantum dot mode-locked laser an attractive source for ultra low noise applications such as optical clocking and optoelectronic oscillators.

The effect of external optical feedback on the linewidth of a single-mode injection laser is considered theoretically. A set of three rate equations with Langevin noise sources is used to obtain the power spectrum. If the high-frequency structure in the power spectrum is ignored, the line shape is Lorentzian and exhibits broadening or narrowing depending on the external-cavity phase shift. Particular attention is paid to the line narrowing after including the effect of carrrier-induced index changes.

By external optical feedback effect on DMLs butt-coupled with a silica-based AWG, we present that 3-dB bandwidths of a DML submodule can be extended to ~37.5 GHz (@ 90 mA) using commercial 28-Gbaud DML chips.

The high frequency modulation effects on the relative intensity noise (RIN) characteristics of 405 nm InAlGaN laser diodes have been investigated taking into account the strain and thermal effects on the laser diode itself as well as external optical feedback effects. The simulation results indicate that the critical external optical feedback for –125 dB/Hz RIN is around 0.1%, a typical order found in practical DVD operating environments.By optimizing the injection current levels and its frequency, one can reduce the RIN with 0.1∼1% external feedback effect by more than 15 dB/Hz. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of external optical feedback on quantum dot two-section passively mode-locked lasers is investigated. The RF linewidth narrows down from 8 KHz in the free-running situation to a very low value of 350 Hz.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text K. Merghem, S. Azouigui, A. Akrout, A. Martinez, F. Lelarge, A. Shen, G. -. Duan, G. Aubin, and A. Ramdane, "RF Linewidth narrowing in Quantum-Dash-Based Passive Mode-Locked Lasers Using Optical Feedback," in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optica Publishing Group, 2009), paper CTuQ3. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

A comprehensive study on the small-signal intensity modulation (IM) characteristics of a fiber grating Fabry-Perot (FGFP) laser is numerically investigated. The effect of external optical feedback (OFB), temperature, injection current, cavity volume, nonlinear gain compression factor, and fiber grating (FG) parameters on IM characteristics are presented. The temperature dependence (TD) of IM is calculated according to the TD of laser cavity parameters instead of using the well-known Parkove relationship. It has been shown that the optimum external fiber length (L ext) is 3.1 cm. The optimum range of working temperature for FGFP laser is between 23 to 27 °C. We also show that by increasing the laser injection current from 10 to 60 mA, the IM peak amplitude decreased from 6.3 to 0.2 dB and the relaxation-oscillation frequency (ROF) is shifted from 1.2 GHz towards higher frequency of 5.48 GHz. In addition, the AR coating reflectivity and gain compression factor have no significant effect on the IM. The study indicates that a stable operation and excellent modulation characteristic can be obtained after optimization process.

A new dual-frequency Doppler lidar (DFDL) system is proposed by using a periodic window with Period-6 of laser dynamics subjected to optical feedback. This method has a good velocity resolution while providing ease of implementation.

The chaos characteristics of a DFB semiconductor laser subjected to single and double external cavity optical feedback are analyzed experimentally. The results show that the correlation dimension, bandwidth of the chaos generated by one external cavity optical feedback can be expanded by using double external cavity optical feedback. When the laser is subjected to double external cavity optical feedback, the bandwidth with one external cavity feedback is increased from 5.5 GHz to 11 GHz. Correspondingly, the correlation dimension is increased from 2.8 to 3.6. The information of the external cavity length of the chaos generated by double external cavity optical feedback can be masked in the autocorrelation function.

The residual phase noise at close-in to carrier offset frequency is studied for optical links using a laser diode with an external optical feedback. Since the measured FM noise degradation of the modulating signal was found to be insignificantly higher than the expected 20log (n) in dB, the residual phase noise of the laser diode was measured to quantify the expected carrier signal FM noise floor level. The measured residual phase noise of a InGaAsP laser diode at 1 KHz offset carrier signal of 5.08 GHz is measured to be -100 and -90 dBc/Hz with and without a 3-cm-long free-space external cavity, respectively. The close-in to carrier phase noise results of this laser at the external cavity resonance frequency of /spl ap/5 GHz is explained for the first time in terms of laser diode nonlinearity and FM noise theory of injection locked microwave oscillators. A good match between the predicted and measured results was observed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

It is shown by computer simulation and in experiments that chaotic generation caused by the external optical feedback in a laser diode can be suppressed by means of a delayed optoelectronic feedback controlled by the injection current. The suppression of chaotic generation is realized for an AlGaAs/GaAs laser of the quantum wall structure. In the presence of the external optical feedback provided by the mirror placed at a distance of 1~mm the noise of optical intensity is of the oder of 10 μW, the single mode dominates in the spectrum, and its spectral width exceeds 600 MHz. The optoelectronic feedback controlled by the injection current reduces the noise by several times and narrows the generation line width down to 80 MHz.

The noise performance of the beat note generated by a dual-polarization fiber grating laser is very critical for sensing applications. To reduce the noise of the beat note, external optical feedback is employed with a fiber Bragg grating as a reflector. It then shows that a longer feedback time results in larger noise reduction. With a 50 m single mode fiber as the delay line, more than 20 dB phase noise reduction has been achieved for a dual-polarization fiber grating laser which shows a phase noise of -92 dBc/Hz @ 10 kHz offset with external optical feedback applied.

This work focuses on the effects of external feedback on the transient response of antiresonant reflecting optical waveguide (ARROW) vertical cavity surface emitting lasers (VCSELs). The study uses a self-consistent system, which is incorporated by the field transfer matrix method, laser rate equations and the reflective index change model, to simulate the dynamics of the VCSELs under optical feedback.

InGaAs/AlGaAs based broad stripe LDs that have failed during the operation with external optical feedback has been investigated. Unusual failure which is accompanied by the extension of DLD from rear-facet to front has been confirmed. Failure mechanism of rear-facet DLD is discussed.