We numerically investigate the modulation dynamics in an integrated three-section MOPA using a voltage driven traveling-wave model. The three-section device includes a distributed feedback laser, a ...modulation section, and a high power tapered amplifier. Both small and large modulation signals are considered, as well as binary data with pseudorandom sequences. The results indicate that dynamic responses of the modulation and amplification sections produce counteracting effects, giving rise in some cases to a reduced chirp, a faster step response, and a decrease of the patterning effects in comparison with the behavior of a single amplifier. In addition to the speed of the carrier response, two dynamical effects are relevant: the reverse current dynamics in the modulation section and the gain saturation dynamics in the amplifier section.
In this work we perform a theoretical and simulation analysis of the behavior of an integrated four section distributed Bragg reflector semiconductor laser under optical injection and Q-switching ...operation. An electro-absorption modulator is introduced into the laser cavity to control the total losses and perform Q-switching. The simulations are done using a rate equation model. Q-switching operation produces very short and high power pulses. This, together with the use of optical injection, allows obtaining flat and broad optical frequency combs with up to 2100 optical lines within 10 dB (642 lines within 3 dB) at a repetition frequency of 100 MHz. The high chirp of the pulses is responsible for the broad spectra of these combs in comparison with gain switched combs, and the device structure allows fabrication in commercial foundries using standard building blocks.
•Optical Frequency Comb generation from semiconductor lasers systematically analyzed.•Gain-switching conditions are determinant for the Frequency Comb quality.•Optical injection may improve or ...deteriorates the Optical Frequency Comb quality.•Comb coherence relies on non-full extinction of stimulated emission between pulses.•Condition to optimize the Comb quality clearly identified.
A systematic experimental study of the generation of Optical Frequency Combs (OFCs) by gain switching two types of edge emitting semiconductor lasers (Distributed Feedback and Discrete Mode) is presented. High resolution spectral measurements together with linewidth characterization and the analysis of the temporal profiles and the radio-frequency spectra are used to evaluate the evolution of the quality of the OFCs, as a function of the driving conditions. Different types of emission spectra are identified. The physical origin of the OFC properties is discussed. The results indicate that the driving conditions rather than the device properties determine the OFC quality. The optical injection is demonstrated to either improve or deteriorate the quality of the OFCs generated by gain switching, depending on the injection conditions.
We demonstrate carbon dioxide sensing using a random-modulation continuous-wave differential absorption lidar transmitter based on an indium phosphide photonic integrated circuit. We have designed ...and characterized the photonic circuit that has been fabricated through an open access generic integration platform based on standard building blocks. It consists of three four-section distributed Bragg reflector lasers, two fast photodiodes, two electro-absorption modulators and five semiconductor optical amplifiers integrated together with several couplers and waveguides. The circuit contains two interrelated subsystems, one for performing the differential absorption lidar measurement, and the other for stabilizing the emission wavelength of the different lasers. We characterize the individual integrated devices, especially lasers, photodiodes and modulators. The carbon dioxide sensing is done by measuring a gas cell in a fiber setup emulating a lidar configuration. Our promising results pave the way to miniaturized differential absorption lidar systems, while highlighting some of the main challenges to overcome.
We present the design and characterization of an integrated optical frequency shifter based on an IQ modulator featuring standard building blocks from a generic photonic integration Indium Phosphide ...(InP) foundry. The device is conceived to be used in applications with low bandwidth requirements such as dual-comb spectroscopy or integrated low-cost LiDARs. An initial analytical study of the system was carried out and subsequently validated by simulations. Then, we obtained experimentally the most relevant parameters of the system and evaluated its performance under frequency shifter operation. Good performance up to 250 MHz is achieved, thus proving its suitability for the intended applications.
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•We have designed and characterized an integrated frequency shifter based on InP.•The PIC design has been made using standard Building Blocks from a generic integration InP foundry.•The device performs well up to 250 MHz, making it suitable for the intended applications.•The design allows to perform a comprehensive characterization of the system through internal PDs.•An analytical model has been proposed considering the layout and the fabrication tolerances.
This paper reports the development of a dual-comb spectroscopy system based on gain-switched single-mode laser diodes emitting at 1572 nm. The switching is performed by a train of short electrical ...pulses at a repetition rate of 100 MHz while the lasers are subjected to external optical injection. Under these conditions, broad and Hat optical frequency combs (OFC) are generated, showing 500 tones within 10 dB and a line spacing fix ed by the repetition rate of the swi tching pulses. The dual-comb gene rated by th e interference of two such combs with slightly different line spacing, is used for measuring the absorption line of CO
2
at 1572.02 nm. The transmission spectrum is analyzed and fitted to a Voigt profile. A deviation of 3% in the residuals of the fitting is obtained, denoting the high spectral performance of the spectroscopy system.
We propose an integrated path differential absorption (IPDA) lidar system based on a hybrid master oscillator power amplifier (MOPA) and single photon counting detection for column-averaged ...measurements of atmospheric CO 2 . The random modulated continuous wave (RM-CW) approach has been selected as the best suited to the average output power obtained from hybrid and monolithically integrated MOPAs. A compact RM-CW IPDA lidar instrument has been designed and fabricated. High-sensitivity and low-noise single photon counting has been used for the receiver. Colocated 2-km horizontal trial path experiments with a pulsed system and in situ measurements were performed for comparison. The RM-CW IPDA lidar instrument shows a relative accuracy of the order of about ±10% or ±40 parts per million CO 2 concentration in absolute terms. The measurements qualitatively demonstrate the feasibility of CO 2 IPDA measurements with an RM-CW system.
We present a voltage driven traveling-wave model for the simulation of an integrated three-section master oscillator power amplifier. The model considers the applied voltage to each active section as ...an input parameter and calculates the longitudinal profiles of the local current and carrier densities. The model reproduces the experimental evidence of either a positive current when the section is acting as an amplifier or a negative current when it is acting as a photodiode in the photovoltaic mode. We validate the model by comparing with experimental results obtained both, under static operation for a variety of biasing conditions and under direct modulation.
This paper reports the development of a dual-comb spectroscopy system based on gain-switched single-mode laser diodes emitting at 1572 nm. The switching is performed by a train of short electrical ...pulses at a repetition rate of 100 MHz while the lasers are subjected to external optical injection. Under these conditions, broad and Hat optical frequency combs (OFC) are generated, showing 500 tones within 10 dB and a line spacing fix ed by the repetition rate of the swi tching pulses. The dual-comb gene rated by th e interference of two such combs with slightly different line spacing, is used for measuring the absorption line of CO2 at 1572.02 nm. The transmission spectrum is analyzed and fitted to a Voigt profile. A deviation of 3% in the residuals of the fitting is obtained, denoting the high spectral performance of the spectroscopy system.
•Generation of high-quality OFCs in optically injected laser diodes by pulsed gain-switching.•Cost-effective SRDs used as electrical generators produce OFCs with 900 tones spaced by 100 MHz.•The ...optical injection does not affect evenly all the tones, leading to a relatively non-uniform OFC.•Timing jitter of the electrical source has been demonstrated to impact the quality of the OFCs.•The use of SRDs reduces the cost, size and footprint of the low repetition rate OFC generators.
We report on the experimental generation of high-quality Optical Frequency Combs (OFCs) at low repetition rates in an externally-injected gain-switched semiconductor laser using a Step-Recovery Diode (SRD) as the pulsing source. The use of an SRD as the electrical pulse generator allows us to produce high-quality OFCs with over 900 comb tones spaced by 100 MHz. Through experimental measurements, supported by simulations, the timing jitter of the electrical source has been demonstrated to impact the quality of the generated OFCs giving rise to a non-uniform Carrier-to-Noise Ratio which is higher around the injection and reduces with decreasing frequency. Nevertheless, comparing the OFC quality obtained using an SRD with those obtained with a costly pulse pattern generator, we conclude, that despite the slightly degraded OFC quality, the use of SRDs could reduce the cost, size and footprint of the equipment required for low repetition rate OFC generation.
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