Wide Wavelength Tuning Research Articles

Monolithic beam steering in a mid-infrared, surface-emitting, photonic integrated circuit

The mid-infrared (2.5 < λ < 25 μm) spectral region is utilized for many purposes, such as chemical/biological sensing, free space communications, and illuminators/countermeasures. Compared to near-infrared optical systems, however, mid-infrared component technology is still rather crude, with isolated components exhibiting limited functionality. In this manuscript, we make a significant leap forward in mid-infrared technology by developing a platform which can combine functions of multiple mid-infrared optical elements, including an integrated light source. In a single device, we demonstrate wide wavelength tuning (240 nm) and beam steering (17.9 degrees) in the mid-infrared with a significantly reduced beam divergence (down to 0.5 degrees). The architecture is also set up to be manufacturable and testable on a wafer scale, requiring no cleaved facets or special mirror coating to function.

34 nm-wavelength-tunable picosecond Ho3+/Pr3+-codoped ZBLAN fiber laser.

We propose and demonstrate a broadly wavelength-tunable mode-locked Ho3+/Pr3+-codoped ZBLAN fiber laser operating in the 3 μm mid-infrared spectral region based on a semiconductor saturable absorber mirror. Wavelength selection is realized by rotating a plane ruled grating. The fiber laser exhibits stable continuous-wave mode-locking operation over a wide wavelength tuning range of 34 nm (2842.2 nm~2876.2 nm), with a 10.17 MHz repetition rate and 22 ps pulse duration. Stable mode-locked pulses can be maintained until the launched pump power of 1.25 W. Maximum average output power of 127.7 mW and the corresponding pulse energy of 12.56 nJ are achieved. To the best of our knowledge, this is the first demonstration of a wavelength-tunable mode-locked fiber laser operating in the 3 μm spectral region. Such simple, robust, and versatile mid-infrared picosecond laser source can find various applications in laser surgery, spectroscopy, and nonlinear frequency conversion.

Tunable ultraflat optical frequency comb generator based on optoelectronic oscillator using dual-parallel Mach–Zehnder modulator

A tunable ultraflat optical frequency comb generator based on the optoelectronic oscillator (OEO) using a dual-parallel Mach–Zehnder modulator (DPMZM) is proposed and experimentally demonstrated. By incorporating a tunable DPMZM-OEO, five comb lines were generated with frequency spacing from 5 to 12 GHz under a wide central wavelength tuning from 1530 to 1560 nm, and a comb flatness of 0.3 dB is obtained. The corresponding signal generated by the DPMZM-OEO is also measured, and the phase noise of the frequency tunable signals is as low as −125 dBc/Hz at 10-kHz frequency offset.

Versatile, high-power 460 nm laser system for Rydberg excitation of ultracold potassium.

We present a versatile laser system which provides more than 1.5 W of narrowband light, tunable in the range from 455-463 nm. It consists of a commercial titanium-sapphire laser which is frequency doubled using resonant cavity second harmonic generation and stabilized to an external reference cavity. We demonstrate a wide wavelength tuning range combined with a narrow linewidth and low intensity noise. This laser system is ideally suited for atomic physics experiments such as two-photon excitation of Rydberg states of potassium atoms with principal quantum numbers n > 18. To demonstrate this we perform two-photon spectroscopy on ultracold potassium gases in which we observe an electromagnetically induced transparency resonance corresponding to the 35s1/2 state and verify the long-term stability of the laser system. Additionally, by performing spectroscopy in a magneto-optical trap we observe strong loss features corresponding to the excitation of s, p, d and higher-l states accessible due to a small electric field.

Full C-Band Tunable V-Cavity-Laser Based TOSA and SFP Transceiver Modules

We report the latest development in tunable transmitter optical sub-assembly (TOSA) and small form-factor pluggable (SFP) transceivers based on simple and compact V-cavity laser (VCL), aiming for low-cost deployment in metro, access, and data center networks. The VCL employs a half-wave coupler to achieve high side-mode suppression ratio (SMSR) and the Vernier effect to achieve a wide wavelength tuning range. Full C-band tuning from 1529.55- to 1566.31-nm with SMSR above 36 dB is demonstrated. Since the laser does not involve any grating or epitaxial regrowth, and has a simple tuning algorithm, it allows simpler processes for fabrication and testing as compared with other widely tunable laser structures. Compact TOSAs and SFP transceiver modules have been developed for full C-band tuning with up to 93 channels at 50 GHz spacing. Transmission experiments are carried out for direct modulation with data rates from 2.5 to 8.5 Gbps. The results of reliability tests of the modules are also presented.

Over 5-W Passively Q-Switched Mid-Infrared Fiber Laser With a Wide Continuous Wavelength Tuning Range

We report efficient high-average-power, high-energy passively Q-switched operation of an Er3+-doped fluoride fiber laser at room temperature with wavelength-tunable resonator configuration utilizing a plane ruled grating for wavelength selection. The fiber laser produced stable Q-switched pulses with a maximum average output power of 5.16 W at 2811.7 nm and a maximum pulse energy of $27.7~\mu \text{J}$ at 2834.6 nm for 30.5-W launched pump power and could be tuned over a wavelength range of 90 nm from 2762.5 to 2852.5 nm, with > 4-W average power over the range of 76.1 nm. Our results present fivefold increase in output power over previously published values directly attained from ~3- $\mu \text{m}$ passively Q-switched fiber lasers and firmly establish a fiber laser as a compact, wavelength-tunable, multiwatt, tens of microjoules mid-infrared pulse source with large scope of both industrial and scientific applications.

Performance of Widely Tunable Multi-Quantum-Well and Bulk Laser Diodes and the Main Limiting Factors

The output power and tuning performance of multi-quantum-well (MQW) and bulk InGaAsP/InP-distributed Bragg reflector (DBR) tunable laser diodes (TLDs) are investigated over a wide wavelength tuning range using physics-based PICS3D and VPI laser simulation tools within the travelling-wave formalism. The key result of our simulations is the discovery of a new effect in TLDs due to intervalence band absorption (IVBA) in passive phase and DBR sections, which limits the wavelength tuning range. The physical mechanism responsible for such a behavior is a collapse of the spectral-mode selectivity by the DBR due to large IVBA losses in the phase or/and DBR sections. We fundamentally demonstrate different roles played by the IVBA in the active and passive sections of a TLD. It is shown that the IVBA in passive sections and the carrier relaxation broadening (CRB) of the Lorentzian lineshape function in the lasers’ active and passive sections play a crucial role in TLD tuning operation. The IVBA coefficient $\text{k}_{\mathrm {IVBA}}$ and the intraband relaxation time $\tau _{in}$ are the major limiting factors that define the output power variation and the achievable tuning range of the lasers. Both bulk and MQW lasers with small $\text{k}_{\mathrm {IVBA}}$ demonstrate a wide wavelength tuning range above 30 nm, while for large $\text{k}_{\mathrm {IVBA}}$ , the tuning range drops below 10 nm. We show that the output power variation with tuning due to the CRB parameter $\tau _{in}$ is qualitatively different in bulk and MQW TLDs. The TLD tuning and power performance is also strongly affected by the shapes of the net gain and the cavity mirror loss spectra and their mutual positioning with respect to the lasing cavity mode during the tuning. The limiting parameters $\text{k}_{\mathrm {IVBA}}$ and $\tau _{in}$ as well as gain and mirror loss spectra must be thoroughly evaluated in each TLD structure prior to the device design and optimization in order to achieve the best performance in terms of the wavelength tuning and the output power stability.

The prototype of new variable period undulator for Novosibirsk free electron laser

To improve the parameters of the second stage Novosibirsk free electron laser we plan to replace the existing electromagnetic undulator by permanent-magnet variable-period undulator (VPU). The VPUs have several advantages compared to conventional undulators, which include wider radiation wavelength tuning range and an option to increase the number of poles. Both these advantages will be realized in the new undulator under development in Budker INP. There are some technical problems, which have to be solved before this idea can be implemented in practice. To check the solution of these problems we designed and manufactured a small undulator prototype, which has just several periods. In this paper, the results of mechanical and magnetic measurements of this undulator prototype are presented and compared with simulations.

Mid-infrared gas absorption sensor based on a broadband external cavity quantum cascade laser.

We developed a laser absorption sensor based on a pulsed, broadband tunable external cavity quantum cascade laser (ECQCL) centered at 1285 cm-1. Unlike traditional infrared spectroscopy system, a quartz crystal tuning fork (QCTF) as a light detector was used for laser signal detection. Fast Fourier transform was applied to extract vibration intensity information of QCTF. The sensor system is successfully tested on nitrous oxide (N2O) spectroscopy measurements and compared with a standard infrared detector. The wide wavelength tunability of ECQCL will allow us to access the fundamental vibrational bands of many chemical agents, which are well-suited for trace explosive, chemical warfare agent, and toxic industrial chemical detection and spectroscopic analysis.

Bismuth-doped fibre laser continuously tunable within the range from 1.36 to

A single-mode bismuth-doped fibre laser continuously tunable within the wavelength range from 1366 to with the help of an external diffraction grating has been developed. Such a wide wavelength tuning range is achieved by inserting a long-period fibre grating in the laser cavity. The grating smoothes the gain spectrum and thus ensures stable lasing at the edges of the above-mentioned spectral range. The output laser power varies from at the tuning range edges to in the centre upon pumping at with a power of .

Monolithic single mode interband cascade lasers with wide wavelength tunability

Monolithic two-section interband cascade lasers offering a wide wavelength tunability in the wavelength range around 3.7 μm are presented. Stable single mode emission in several wavelength channels was realized using the concept of binary superimposed gratings and two-segment Vernier-tuning. The wavelength selective elements in the two segments were based on specially designed lateral metal grating structures defined by electron beam lithography. A dual-step dry etch process provided electrical separation between the segments. Individual current control of the segments allowed wavelength channel selection as well as continuous wavelength tuning within channels. A discontinuous tuning range extending over 158 nm in up to six discrete wavelength channels was achieved. Mode hop free wavelength tuning up to 14 nm was observed within one channel. The devices can be operated in continuous wave mode up to 30 °C with the output powers of 3.5 mW around room temperature.

ChemInform Abstract: Organometal Halide Perovskite Quantum Dots: Synthesis, Optical Properties, and Display Applications

AbstractReview: 81 refs.

Characteristics and improvement of wideband wavelength-tunable narrow-linewidth source by spectral compression in quasi-dispersion-increasing comb-profile fiber.

We investigated the characteristics and behavior of spectral compression in a quasi-dispersion-increasing comb-profile fiber (CPF). A periodical breathing behavior and sidelobe emission process in the CPF were observed in numerical analysis. Then, taking account of the numerical results, we developed an improved CPF in which the sidelobe suppression was dramatically improved to -24.2 dB while keeping a narrow spectral width of ~0.6 nm. As a seed pulse source, we developed a high-repetition-rate Er-doped ultrashort-pulse fiber laser with single-wall carbon nanotubes and used the improved CPF to realize a high-power, narrow-linewidth source with wide wavelength tunability in the 1.62-1.90 μm band.

Investigation of mode characteristics in rectangular microresonators for wide and continuous wavelength tuning

The mode characteristics are investigated for the rectangular microresonators with an output waveguide connected to the midpoint of the long side for wide and continuous wavelength tuning. Through adjusting the aspect ratio of the rectangular microresonator, the mode Q factors can be greatly enhanced. Furthermore, the large mode interval between the high-Q modes makes the rectangular microresonators suitable for tunable lasers. As a special case, single-mode operation is achieved with a continuous tuning range of 9.1 nm for a square microlaser with the side length of 17.8 mm and the output waveguide width of 1.8 mm.

Engineering non-radiative anapole modes for broadband absorption enhancement of light.

In this paper, we propose a novel, frequency- and angularly- broadband approach to achieve absorption rate enhancement in high-index dielectric nanostructures through the engineering of non-radiative anapole modes. We employ multipolar decomposition of numerically computed current distributions and analyze the far-field scattering power of multipole moments. By leveraging the destructive interference of electric dipole and toroidal dipole moments, we design non-radiating anapole modes and demonstrate significantly enhanced absorbed power in silicon and germanium nanostructures. We demonstrate wide wavelength tunability of the anapole-driven peak absorption enhancement for nano-disks and square nano-pixel geometries, which can be conveniently fabricated with current lithography. Finally, by combining nano-disks and nano-pixels of different sizes into functional surface units, we design nanostructured arrays with enhanced bandwidth and absorption rates that can be useful for the engineering of broadband semiconductor photodetectors driven by controllable anapole responses.

GaAsP tunable distributed Bragg reflector laser with indium tin oxide thin-film heater

A GaAsP quantum well tunable distributed Bragg reflector (DBR) laser with a thin-film heater above a DBR grating was designed and fabricated. As a result of the optimization of the DBR grating to obtain both high reflectivity and sharp wavelength selectivity, single-mode lasing with an output power of 54 mW and a side-mode suppression ratio of 43 dB was obtained. By forming the transparent thin-film heater at a distance of 0.1 µm above the DBR grating, the DBR grating was heated locally and efficiently, and a wide wavelength tuning range of 5.2 nm was achieved by heating with a heater power as low as 160 mW.

Organometal halide perovskite quantum dots: synthesis, optical properties, and display applications

In recent two years, organometal halide perovskites quantum dots are emerging as a new member of the nanocrystals family. From the chemical point of view, these perovskites quantum dots can be synthesized either by classical hot-injection technique for inorganic semiconductor quantum dots or the reprecipitation synthesis at room temperature for organic nanocrystals. From a physical point of view, the observed large exciton binding energy, well self-passivated surface, as well as the enhanced nonlinear properties have been of great interest for fundamental study. From the application point of view, these perovskites quantum dots exhibit high photoluminescence quantum yields, wide wavelength tunability and ultra-narrow band emissions, the combination of these superior optical properties and low cost fabrication makes them to be suitable candidates for display technology. In this short review, we introduce the synthesis, optical properties, the prototype light-emitting devices, and the current important research tasks of halide perovsktie quantum dots, with an emphasis on CH3NH3PbX3 (X = Cl, Br, I) quantum dots that developed in our group.

Lasers for Optogenetics and Multimodal Microscopy

AbstractA new type of short‐pulse ultrafast laser sources provides extremely wide (680 — 1300 nm) wavelength tunability of the primary output as well as simultaneous high power (1.5 watts) output at 1040 nm. This combination makes lasers such as the Chameleon Discovery ideal for demanding multiphoton excitation applications in optogenetics, multimodal imaging, and other microscopy applications that need two independent wavelengths. In this article we will see why these applications benefit from this performance.

Electrons, holes, and excitons in GaAs polytype quantum dots

Single and multi-band k⋅p Hamiltonians for GaAs crystal phase quantum dots are used to assess ongoing experimental activity on the role of such factors as quantum confinement, spontaneous polarization, valence band mixing, and exciton Coulomb interaction. Spontaneous polarization is found to be a dominating term. Together with the control of dot thickness [Vainorius et al., Nano Lett. 15, 2652 (2015)], it enables wide exciton wavelength and lifetime tunability. Several new phenomena are predicted for small diameter dots [Loitsch et al., Adv. Mater. 27, 2195 (2015)], including non-heavy hole ground state, strong hole spin admixture, and a type-II to type-I exciton transition, which can be used to improve the absorption strength and reduce the radiative lifetime of GaAs polytypes.

Tunable nanoblock lasers and stretching sensors.

Reconfigurable, reliable, and robust nanolasers with wavelengths tunable in the telecommunication bands are currently being sought after for use as flexible light sources in photonic integrated circuits. Here, we propose and demonstrate tunable nanolasers based on 1D nanoblocks embedded within stretchable polydimethylsiloxane. Our lasers show a large wavelength tunability of 7.65 nm per 1% elongation. Moreover, this tunability is reconfigurable and reliable under repeated stretching/relaxation tests. By applying excessive stretching, wide wavelength tuning over a range of 80 nm (spanning the S, C, and L telecommunication bands) is successfully demonstrated. Furthermore, as a stretching sensor, an enhanced wavelength response to elongation of 9.9 nm per % is obtained via the signal differential from two nanoblock lasers positioned perpendicular to each other. The minimum detectable elongation is as small as 0.056%. Nanoblock lasers can function as reliable tunable light sources in telecommunications and highly sensitive on-chip structural deformation sensors.