Cristina de Dios

Improvements to Long-Duration Low-Power Gain-Switching Diode Laser Pulses Using a Highly Nonlinear Optical Loop Mirror: Theory and Experiment

This work presents an experimental and theoretical study on the improvements to pulsed diode laser gain-switched (GS) optical sources. Simultaneous compression and reshaping of the limited quality pulses obtained with this technique are reported using a highly nonlinear optical loop mirror (HNOLM) directly coupled to the diode laser source, without any previous pulse conditioning. The HNOLM is based on the use of a microstructured optical fiber and a highly nonlinear semiconductor optical amplifier; it is compact and offers benefits in terms of reduced system complexity. The experimental observations are compared to a theoretical model of the system, and excellent agreement is observed.

Dual optical frequency comb architecture with capabilities from visible to mid-infrared

In this paper, a new approach to dual comb generation based on well-known optical techniques (Gain-Switching and Optical Injection Locking) is presented. The architecture can be implemented using virtually every kind of continuous-wave semiconductor laser source (DFB, VCSEL, QCL) and without the necessity of electro-optic modulators. This way, a frequency-agile and adaptive dual-comb architecture is provided with potential implementation capabilities from mid-infrared to near ultraviolet. With a RF comb comprising around 70 teeth, the system is validated in the 1.5 μm region measuring the absorption feature of H13CN at 1538.523 nm with a minimum integration time of 10 μs.

Understanding VCSEL-Based Gain Switching Optical Frequency Combs: Experimental Study of Polarization Dynamics

In this paper, we carry out an experimental study on the polarization properties of a vertical-cavity surface-emitting laser (VCSEL) working under gain switching (GS) regime and the characteristics of the resulting optical frequency comb signal. We have observed that each of the two polarization modes presented in the VCSEL continuous wave emission spectrum generate a separate optical frequency comb (OFC) whose modes are phase correlated thanks to the GS regime. We study how these combs associated with the main and orthogonal polarization modes, respectively, vary depending on the input parameters to the VCSEL (bias current and radio-frequency power and frequency). The correlation between both OFCs in the best operation point as defined by the OFC characteristics is also evaluated. Therefore, this study demonstrates that two orthogonally polarized combs are generated that exhibit a high correlation between each other that combine to produce a wider overall optical comb. Hence, we can predict the feasibility of dual-polarization VCSEL-based OFC generators in the few gigahertz repetition frequency rates, with highly correlated modes and continuously tunable distance between them, in a compact and energy- and cost-efficient system that can find application in ultrafast laser dynamics studies and or in polarization-division multiplexing optical communications.

Optimum design of NOLM for compression of low power gain-switching pulses

The compression and reshaping of optical pulses is a key issue for many of the applications in which ultrashort optical pulses are present since dispersion, nonlinearity and losses degrade their quality. We present a novel numerical procedure for designing pulse compressors based on Nonlinear Optical Loop Mirrors (NOLM). To exemplify the performance of the model, we apply this tool to the design of a NOLM intended to compress and reshape low energy pulses obtained by means of diode laser pulsed sources. This way, the quality of the pulses generated with this techniques can be improved.

Gain-switching injection-locked dual optical frequency combs: characterization and optimization

In this work, the generation of dual optical frequency combs based on gain-switching and optical injection locking is experimentally examined. The study reveals that an effective process of optical injection can lead to optimized RF combs in terms of span and signal-to-noise ratio. The system also minimizes the overlap of lines and reduces the number of optical components involved, eliminating the need for any external modulator (electro-optic, acousto-optic). The validation of the system was performed as a dual-comb spectrometer, which allowed for determination of the absorption and dispersion profiles of the molecular transition of H13CN at 1538.523 nm.

Expansion of VCSEL-Based Optical Frequency Combs in the Sub-THz Span: Comparison of Non-Linear Techniques

In this study, we detail our experimental study on the expansion of vertical-cavity surface-emitting laser (VCSEL) optical frequency combs (OFCs) with different nonlinear techniques. For this purpose, we modulate a VCSEL device under gain switching (GS) regime to obtain an initial seed comb record in terms of energy efficiency and mode coherence. This seed OFC will be improved adding a nonlinear stage to expand this primary signal. The nonlinear techniques here presented are high nonlinear fibers, nonlinear optical loop mirrors, and electro optical phase modulators. In this study, we show the different extended OFCs that these techniques offer and we present a detailed comparison of their characteristics, evaluating the advantages and disadvantages of each technique. We have observed that the obtained OFCs maintain the high coherence offered by the seed VCSEL-OFC. Nevertheless, the optical span, flatness, frequency tunability, dynamic range, energy, and cost efficiency or compactness of each expanded OFC significantly vary, depending on the expansion technique used. Our careful evaluation will serve as a reference to evaluate the suitability of each expansion technique depending on the needs or the application.

All optical passive stabilization of a two-section InAs/InP based quantum-dash mode-locked laser with simultaneous CW injection-locking and selective optical feedback

We demonstrate narrow pulses with low RF linewidth from two-section InP quantum-dash mode-locked lasers. Simultaneous CW injection-locking and selective optical feedback lead to ≃50 times RF linewidth and 1.5 times time-bandwidth product reduction.

Noise influence in nonlinear optical loop mirror compression performance

Short pulsed laser sources have recently been under investigation for applications in high speed optical communications systems. A key issue to achieve high quality reliable short pulses is the need to compress and improve the shape of the pulse train. Nonlinear Optical Loop Mirrors (NOLM) provides both compression and reshaping of the optical pulses. The present work turns the attention to the influence of noise in the compression behavior of NOLM. Characteristics such as compression factor, signal to noise ratio, dynamic RIN level, BER and timing jitter are considered. The results obtained will be the basis for the design of a compact high quality ultrashort optical pulse source at 40 GB/s with monolithic semiconductor compressor. This device is under investigation within the MONOPLA European Project.

Comparative study of nonlinear optical loop mirror using gain switching diode lasers

Generation of high quality ultrashort optical pulses for optical communications in the 1,55 μm window is an important field of study. A key issue is the need to compress pulse width. Several techniques provide this compression functionality. Nonlinear Optical Loop Mirrors provide both compression and reshaping of the optical pulses. This work presents a comparative numerical study of several NOLM schemes whose results will be the basis for the design of a compact high quality ultrashort optical pulse source at 40 GBs with a monolithic InP semiconductor compressor. This source is under investigation within the MONOPLA project. A model based on the Nonlinear Schrödinger Equation is used. Input pulses are considered to be generated by a Gain Switching diode laser source. Characteristics such as time-bandwidth product, peak-power, pulse shape and pedestals are being considered.

Fully remote rapid multiheterodyne spectroscopy based on the remote detection of an optical frequency comb through optical injection locking and electro-optic comb generation

The potential of Optical Frequency Combs (OFC) as wide bandwidth, stable, coherent, multimode sources is widely recognized and has applications in various fields, such as metrology, spectroscopy, optical communications or biomedicine. The dual optical frequency comb approach relies on the use of a second local oscillator (LO) comb with slightly different repetition frequency. This LO is then heterodyned with the primary comb to generate a down-converted RF comb from which the spectral information is retrieved. The dual-comb approach results in ultra-fast measurement times while maintaining the OFC capabilities concerning resolution, bandwidth and stability [1].