Dual and multi-wavelength lasers, i.e., lasers with the ability to emit at two or more wavelengths in a controlled fashion, represent an exciting new twist in laser physics. Harnessing the mode competition to control them better remains, however, a challenge. In this work, we numerically explore the effect of optical feedback on the emission properties of a dual-wavelength laser using a rate equation model. We focus on switching capability and investigate the impact of key laser and feedback parameters. We connect the emergence of simultaneous emission to a lower cross-saturation between modes, and demonstrate that robust switching can be achieved using a short feedback cavity and a sufficiently strong feedback. In particular and in contrast to previous publications, we highlight that the feedback phase difference between the two modes is not a critical parameter. Our results are consistent with recent experimental observations, supporting the relevance of feedback-based control techniques for multi-wavelength lasers.

All-optical wavelength conversion (AOWC) is a key functionality for future wavelength-division multiplexing (WDM) networks, enabling signal routing and wavelength reassignment without power-hungry optoelectronic regeneration. AOWC mostly relies on nonlinear interactions between the signal and a pump in a semiconductor optical amplifier (SOA). Here, we demonstrate AOWC using a monolithically integrated indium phosphide (InP) multi-wavelength laser (MWL), eliminating the need for an external probe laser. By optically injecting an intensity-modulated data signal into the MWL, carrier-induced gain modulation in the shared gain section, together with strong intermodal coupling between longitudinal modes, enables data wavelength conversion over a 1.3 THz range for signals up to 10 GBd. A monolithically integrated feedback cavity provides agile selection among three output modes or simultaneous broadcasting across all three, by tuning the feedback phase. We evaluate the signal quality of the converted data for various symbol rates, showing both transparent conversion and, at low injection powers, net signal gain. Complementary numerical simulations, based on a multimode extension of the Lang-Kobayashi rate equations, reveal the role of modal gain imbalance and cross-saturation in shaping the conversion efficiency. These results point to a scalable, compact, and energy-efficient route toward agile AOWC devices. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

We investigate discrete wavelength switching in single-gain-section multi-wavelength lasers monolithically integrated on InP with phase-controlled optical-feedback. By modulating the feedback phase, nanosecond-scale wavelength switching is experimentally demonstrated with transition times below 2.5 ns. Measurements consistently show that the switching time decreases with stronger optical feedback and larger phase-modulation amplitudes. Transitions from lower to higher modal gain are faster. We support the experimental observations with a multi-mode extension of the Lang-Kobayashi rate-equation model. We analyze the influence of laser, feedback-cavity, and modulation parameters on the switching dynamics, and highlight the role of mode coupling. These results highlight the potential of integrated multi-wavelength lasers for compact and high-speed all-optical networking systems.

We present a monolithic, diffractive beam splitter fabricated directly on a single-mode fiber facet using two-photon polymerization-based direct laser writing. The device acts as a proof of concept for coupling between single-mode and multi-core fibers using beam shaping and free-space projection over 40 mu m. Using a waveguide-based mode expansion up-taper and diffractive optical elements, the input beam is split into seven beams over a full angular spread of 72(degrees), and the outputs are collimated over a total structure length of 355 mu m and a footprint of 115 mu m diameter. The concept enables miniaturization of single-mode to multi-core fiber interfacing, for communication and lab-on-fiber applications.

We demonstrate all-optical wavelength conversion over a 1.3 THz range for signals of up to 10 GBd using cross-gain modulation (XGM) in an integrated multi-wavelength laser (MWL). Our approach enables agile control of the wavelength shift without requiring additional probe lasers while achieving high conversion efficiency. The MWL, designed with a dual-cavity structure and a single gain section, supports dynamic wavelength switching at the nanosecond time scale. These features make our solution highly suitable for WDM networks.

Tunable lasers are essential and versatile tools in photonics, with applications spanning telecommunications, spectroscopy, and sensing. Advancements have aimed to expand tuning ranges, suppress mode hopping, and enable photonic integration. In this work, we explore the adaptation of dynamic targeting, a technique originally developed to stabilize lasers under optical feedback, as a method for achieving agile, fast, and continuous wavelength tuning. By adjusting the feedback rate and phase, we enable a stable and controlled frequency shift. We experimentally demonstrate reliable and reproducible tuning over 2.1 GHz using a free-space optical setup. Simulations further suggest that this approach could extend the tuning range to tens of GHz, with a potential scan speed exceeding 10^17 Hz/s. These results highlight dynamic targeting as a promising route toward agile frequency control in semiconductor lasers.

Vertical-Cavity Surface-Emitting Lasers (VCSELs) combine compact geometry, low threshold current, and ease of integration, making them central to modern photonic systems. However, their polarization behavior remains a critical factor affecting performance, as the emission state can switch between orthogonally polarized modes around the so-called polarization switching point. This regime exhibits high sensitivity, where small perturbations induce abrupt polarization changes and nonlinear responses. In this work, the polarization dynamics of VCSELs under sinusoidal current modulation around the switching point are numerically investigated using the Spin-Flip Model. The study examines the influence of modulation frequency, amplitude, and bias current, revealing distinct dynamical regimes including polarization locking, periodic and irregular switching. The observed transitions between regimes elucidate the interplay between modulation and polarization stability, providing insight into the control of VCSEL dynamics for high-speed optical communication and sensing applications.

Semiconductor lasers subject to optical feedback can behave chaotically, which can be used as a source of randomness. The optical feedback, provided by mirrors at a distance, determines the characteristics of the chaos and thus the quality of the randomness. However, this fixed distance also shows itself in the intensity, an unwanted feature called the Time Delay Signature (TDS). One promising solution to suppress the TDS is using double optical feedback. We study this system numerically in this paper. In particular, we focus on the impact of the feedback phase, a sub-wavelength change in the position of the mirrors, on the TDS and chaos bandwidth (CBW) of the system. We show that by precisely setting the feedback parameters, including the feedback phases, the TDS can be suppressed, and that the feedback phase control is necessary rather than optional to robustly suppress the TDS. In addition, it is possible to suppress the TDS without loss of the CBW. At strong feedback rates the system can restabilize, and one can switch between a chaotic and steady state by changing only the feedback phase. Finally, we relate the feedback phase sensitivity to interference between the two delayed signals. This system is promising for applications of chaotic lasers as one can either suppress the TDS or increase the CBW.

Single-mode semiconductor lasers subject to optical injection have been shown to trigger a wide range of dynamical behavior from injection locking to chaos. Multi-wavelength lasers add even more degrees of freedom and complexity to the dynamical repertoire potentially unlocking new functionalities for applications ranging from THz generation and processing to all-optical memories. In particular, leveraging the inherent mode coupling in multi-wavelength lasers, spectral multiplication over a THz range of an injected optical signal has been shown. While most of the research on optical injection has been focused on single-mode semiconductor lasers, the dynamical behavior of multi-wavelength lasers, particularly when subjected to injection of amplitude-modulated signals remains vastly unexplored. In this work, we numerically and experimentally investigate the response of an on-chip dual-wavelength laser subject to the optical injection of a single-sideband signal around one of the modes of the laser. Our findings show an asymmetric power evolution of the sidebands appearing around both the injected and un-injected modes with respect to the modulation frequency. The power and bandwidth of the sideband signals strongly depend on the resonance frequency produced by the interference between the cavity mode and the injection, which can be tailored by twerking the strength and the detuning of the injection. The outcomes of our numerical investigations, based on rate equations, align closely with the experimental results highlighting the influence of key injection and laser parameters.

With increasing demands on data processing speeds and the correspondingly high requirements for data transfer bandwidth, research is focusing on replacing pluggable optical transceivers with co-packaged optics architectures. Vertical-cavity surface-emitting lasers (VCSELs) have been considered a promising candidate in such configurations, but traditional optoelectronic packaging approaches-such as flip-chip and wire-bonding-fall short of meeting the low-cost and high-speed requirements. In this paper, we present the integration of bare-die VCSEL arrays into femtosecond laser-fabricated fused silica microwells, combined with direct on-VCSEL fabrication of micro-optics using two-photon polymerization-based direct laser writing. The 1 x 4 VCSEL arrays, operating at a wavelength of 850 nm, are aligned in a face-up configuration and are electrically interconnected within a 5.5 mu m passivation layer with photolithographically defined copper tracks. Efficient beam shaping is demonstrated by 3D nanoprinting 200 mu m tall refractive and diffractive focusing microlenses directly onto the integrated VCSELs with an in-plane pitch of 250 mu m. The emitted beams are focused into a 5 mu m diameter Gaussian spot and are efficiently coupled into a single-mode fiber. This scalable packaging approach highlights the potential for compact, high-density solutions for co-packaged optics architectures with glass interposers.

Wavelength conversion is key for wavelength division multiplexing (WDM) networks [1], e.g., to enable flexible wavelength allocation within subnetworks. In current implementations, signal routing impacts the latency and power consumption due to necessary optoelectronic conversions [2]. To overcome this bottleneck, all-optical techniques have been proposed: most relying on nonlinearities in semiconductor lasers or amplifiers, such as four-wave mixing and difference-frequency generation [3]. But these methods require additional probe lasers [4], phase matching [1], and generally feature low conversion efficiency. In this work, we take a different approach: we use a custom multi-wavelength laser (MWL) to achieve emission at the desired wavelength spacing, thus removing the need for probe signals.

The growing demand for higher data transmission rates and the increased use of THz signals for spectroscopy and sensing application motivates interest in mm-wave and THz technologies [1]. High-capacity THz wireless communications systems, among others require the ability to manipulate and process such signals. But, due to the limited bandwidth of electronics systems, photonic-based solutions are promising to enable THz-optical-THz conversion, bringing the processing to the optical domain [2]. In this work, using an on-chip photonic system, we demonstrate narrowband filtering and amplification of optical signals that could be directly applied to THz all-optical signal processing.

We present a novel method for integrating Vertical Cavity Surface Emitting Lasers (VCSELs) into fused silica glass, combining precise embedding with the direct laser writing of polymer-based micro-optic elements. Custom-shaped cavities for GaAs-based VCSEL arrays (850 nm) are formed via femtosecond laser irradiation and chemical etching. An electrical redistribution layer is created using polyimide coating, excimer laser via-drilling, TiW-Cu sputtering, and photolithographic patterning. Micro-optics for beam focusing are designed, fabricated via two-photon polymerization directly on the integrated VCSELs, and characterized.

This study investigates the impact of controlled mechanical strain on the wavelength and birefringence characteristics of Vertical-Cavity Surface-Emitting Lasers (VCSELs), key components in optoelectronics, especially in data centers. Utilizing a custom four-point bending module, we systematically analyze the effects of strain on VCSELs, focusing on wavelength evolution and birefringence tuning. Our experiments reveal a consistent blue shift in the laser’s wavelength, up to 1 nm, correlating linearly with applied strain levels of approximately 0.271 nanometer / milli strain. Additionally, birefringence tuning from 100 GHz to 290 GHz is achieved, demonstrating the potential of strain manipulation as a reliable technique for precise wavelength and birefringence adjustments. These findings suggest significant prospects for enhancing VCSEL performance in optical communication applications, allowing for optimized performance and expanded functionality in various optoelectronic systems.

In this report, we experimentally analyze the effect of optical injection of a signal with a single-sideband (SSB) modulation on a multi-wavelength laser (MWL) integrated on a photonic integrated circuit. The optical injection of an SSB modulation into the MWL leads to spectral multiplication of the signal around the un-injected modes of the MWL. This multiplication arises from the modulation of the carrier density inside the cavity and the strong nonlinear coupling between different modes of the MWL. We report an asymmetric power evolution of the generated sidebands around the injected and un-injected modes of the MWL while the modulation frequency is swept. The power and modulation bandwidth of the signal emerging around the injected and un-injected modes strongly depend on the position of the cavity resonance frequency of the injected mode, which can be tailored by adjusting the injection strength and the detuning of the injected signal.

This study investigates the influence of controlled mechanical strain on the wavelength characteristics of Vertical-Cavity Surface-Emitting Lasers (VCSELs), crucial components in optoelectronics, particularly in data centers. Using a custom four-point bending module, we systematically analyze the impact of strain on VCSELs by examining the wavelength evolution under varying strain levels. we report a consistent blue shift in the laser's wavelength with increasing strain while maintaining stable power output. These findings highlight the potential of strain manipulation as a reliable technique for wavelength tuning in VCSELs, offering prospects for enhancing their performance in optical communication applications.

Optical frequency combs (OFCs) have been identified as a key building block for many applications ranging from spectroscopy to optical communications. In these applications, the fixed phase relation between the individual spectral components of the comb is a crucial aspect of frequency combs. Recently multi-wavelength lasers that are in essence multimode lasers have shown a promising capability to enable frequency comb multiplication over a broad range of frequency offsets surpassing 1 THz. Despite the robust phase coherence within each comb's lines, there remains a notable lack of phase coherence among distinct sub-combs. In this work, we show that the injecting of an adapted frequency comb, i.e., a narrowband comb comprising five lines and an extra tone separated by a certain frequency offset from the central line of the comb, facilitates cascaded phase locking between three adjacent sub-combs. The interaction between the regenerated comb and the multiplied comb induced by the extra tone initiates a modulation at their beating frequency. By fine-tuning the frequency of the extra tone, we can adjust the position of the resulting beating, and eventually achieve a cascaded phase locking for the third mode. We envision that cascaded phase-locking can advantageously be extended to additional modes leading to cover higher frequency offsets up to a few THz.