Tunable Ring Research Articles

Monolithically Integrated Tunable Laser Using Double-Ring Resonators With a Tilted Multimode Interference Coupler

A monolithically integrated tunable semiconductor ring laser consisting of a semiconductor optical amplifier and two ring resonators with tilted multimode interference (MMI) couplers is presented. The characteristic response of the ring resonators is discussed for various cross coupling strengths by adjusting the angle of the tilted MMI couplers. The ring laser has a wavelength tuning range of 11 nm and a sidemode suppression ratio larger than 40 dB for a cross coupling strength of 0.09. The peak power of the laser is larger than -3 dBm for chip-to-fiber coupling.

Tunable microwave devices based on left/right-handed transmission line sections in multilayer implementation

Metamaterial transmission lines can be realized as a combination of right- and left-handed transmission line (TL) sections exhibiting positive and negative dispersion. This approach gives additional degrees of freedom for improving the performance of microwave devices. Artificial right- and left-handed sections, which are based on lumped-element unit cells consisting of inductance and capacitances (LC-cells), are used. This makes it possible to decrease dimensions of the devices drastically. Furthermore, using variable capacitors in LC-cells allows designing tunable devices. This paper presents the results of design, numerical simulation, and experimental investigation of a tunable rat-race ring and free-of-spurious response dual-band filter manufactured as integrated ceramic multilayer circuits based on low-temperature co-fired ceramics. Commercial semiconductor varactors have been used as tunable components.

Self-adaptive, narrowband tuning of a pulsed optical parametric oscillator and a continuous-wave diode laser via phase-conjugate photorefractive cavity reflectors: verification by high-resolution spectroscopy

A dynamic self-adaptive Bragg grating formed in a photorefractive crystal is shown to be a convenient way to attain single-longitudinal-mode (SLM) operation and narrowband tuning both in a pulsed, injection-seeded optical parametric oscillator (OPO) and in a continuous-wave (cw) extended-cavity diode laser. The pulsed OPO cavity comprises a Rh:BaTiO3 photorefractive (PR) crystal, a periodically poled KTiOPO4 nonlinear-optical crystal, and a dielectrically-coated end mirror. A continuous-wave seed beam at 820–850 nm from a tunable SLM diode laser traverses firstly the Rh:BaTiO3 crystal and then is retro-reflected by the end mirror; this creates a wavelength-selective Bragg grating reflector in the PR crystal, thereby completing the OPO cavity. The cavity stays automatically resonant with the seed radiation, with no need to actively control its length or to make any other mechanical adjustment. One form of injection seeder comprises a novel extended-cavity diode laser (ECDL) design incorporating a self-pumped photorefractive phase-conjugate reflector and a compact, high-finesse tunable intracavity ring filter. This combination facilitates robust tunable single-frequency operation with narrow optical bandwidth. The performance characteristics of the OPO and the ECDL are evaluated by recording high-resolution atomic and molecular spectra. Notably, fluorescence-detected sub-Doppler two-photon excitation at 822 nm, of the 8S←6S transition in atomic Cs, provides a crucial linewidth test.

Low-Loss and Low-Birefringence High-Contrast Silicon-Oxynitride Waveguides for Optical Communication

Silicon-oxynitride waveguides fabricated by plasma-enhanced chemical vapor deposition are very attractive for passive optical components used in optical networks. We use a combination of an high-index contrast and compact core dimensions for the realization of small bending radii. To achieve the high quality requirements with the desired waveguide design the layer deposition and the waveguide fabrication are optimized. Furthermore, we discuss the interface of the high-index optical components to standard single-mode fiber (SSMF) and coupling tolerances, which is more difficult compared to common fiber-mode-matched wave guides. We show results of fabricated Mach-Zehnder interferometer-switches, tunable ring resonators and present a solution to reduce the waveguide birefringence by adjusting the mechanical stress of the cover layer.

Tunable Channel Spacing of Dual-wavelength Erbium-doped Fiber Ring Laser using a Single Fiber Bragg Grating with Two Coil Heaters

Stable and tunable dual-wavelength erbium-doped fiber ring laser (EDFL) using a single fiber Bragg grating (FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 ㎚ of wavelength under the electrical power with a 1000 ㎽. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

On chip tunable micro ring resonator actuated by electrowetting

We demonstrate a tunable on chip polymer waveguide micro ring resonator (MRR) device. The transmission spectrum and extinction ratio are controlled by electrowetting on dielectric (EWOD), via the application of voltage to a droplet. As a result the droplet covers a portion of the MRR waveguide and changes its effective refractive index. This method can be used for efficiently tuning a variety of on chip optical devices, as it offers high index contrast, electrical control and low power consumption.

Research on tunable erbium-doped ring fiber laser based on a high-birefringence Sagnac loop: theory and experiment

A simple erbium-doped ring fiber laser based on a high-birefringence Sagnac loop filter is proposed. The Sagnac is composed of a polarization controller （PC） and a polarization-maintaining fiber （PMF）. The effect of PC and PMF on tunable laser is analyzed in theory. In experiment， the single， double and multiple wavelength lasers are obtained by adjusting the PC. The interval of wavelength varies with the length of PMF. The experimental results are in good agreement with the theorefical analysis. In experiment the stable laser output with 20% slope efficiency， 0.016 nm 3 dB line-width， 0.097 nm 30 dB line-width and 40 dB SMSR was obtained.

Tunable polymer/silicon over insulator ring resonators

A tunable ring resonator RR formed from Si/SiO2 waveguides with an electro-optic polymer cladding is proposed with em- phasis on the trade-off between the tuning voltage and ring radius. The ring resonator circuit combines the advantages of Si/SiO2 and polymer technologies. The advantages of this hybrid ring design over previously proposed tunable silicon rings include an increased switching speed, from 5 GHz to 20 to 100 GHz, single-polarity instead of dual-polarity voltage tuning and a voltage-independent quality factor. The hybrid de- sign also displays a greater free spectral range 1.85 nm instead of 0.1 nm and a wider tuning range 0.925 nm instead of 0.05 nm and is further compatible with silicon devices. Moreover, the device has a high quality factor of 3.410 4 . © 2008 Society of Photo-Optical Instrumentation

Voltage-tuned multiwavelength Raman ring laser with high tunability based on a single fiber Bragg grating

A practical scheme for a tunable multiwavelength Raman fiber ring laser based on a single fiber Bragg grating with a voltage-controllable coil heater is investigated. The number of phase-shifted regions within a single fiber grating determines the number of reflection peaks and the number of lasing wavelengths in the multiwavelength Raman fiber ring laser. A stable multiwavelength Raman fiber ring laser with low output peak-power fluctuation of less than 0.5 dB at room temperature is achieved. A multiwavelength Raman fiber ring laser with a high extinction ratio of more than 50 dB is realized. High flatness is obtained for three lasing peaks, and the lasing peak-power difference is measured to be less than 0.2 dB. A voltage-controllable coil heater with heating elements is used to effectively control three lasing wavelengths in the multiwavelength output, and the tunability of each lasing wavelength is measured to be 0.11 nm/V.

Widely tunable compact erbium-doped fiber ring laser for fiber-optic sensing applications

A compact erbium-doped ring-shaped fiber laser suitable for fiber-optic sensing applications has been developed. The fiber laser utilized a tunable fiber Fabry–Perot filter as the tuning element and had a moderate milli-Watt level power output over almost the whole tuning range from 1530 to 1595 nm with a power fluctuation of 0.15 dB. High repetition rate scanning of laser operation over the whole tuning range was achieved at rates of up to 200 Hz. Moreover, the performance of the ring-shaped fiber laser configured with a high-concentration erbium-doped fiber was investigated for its larger wavelength tunability of over 100 nm. Output power characteristics of this ring-shaped fiber laser were also investigated when it worked in a scanning mode. A distorted power wavelength dependence, as well as some pulsing phenomenon were observed in scanning mode.

Robust tunable single-frequency operation of a diode laser by a self-pumped phase-conjugate reflector and a high-finesse filter

A novel form of extended-cavity diode laser attains robust tunable single-frequency operation with narrow linewidth. The laser cavity includes a self-pumped photorefractive phase-conjugate reflector for wavelength-adaptive narrowband feedback and a compact high-finesse tunable intracavity ring filter for single-longitudinal-mode selectivity and control. Its performance around 830 nm is verified with a simple Fabry-Perot laser diode and by Doppler-free two-photon spectroscopy in atomic cesium.

Tunable Fiber Laser With Ultra-Narrow Linewidth Using A Tunable Phase-Shifted Chirped Fiber Grating

We experimentally demonstrate a tunable C-band erbium-doped fiber ring laser with ultra-narrow linewidth using a tunable phase-shifted linearly chirped fiber Bragg grating (PS-LCFBG) as an intracavity ultra-narrowband filter. The center wavelength of the PS-LCFBG with an ultra-narrow bandwidth of 30 dB, an output power of ~10 dBm, a small power variation of <0.2 dB, and a small wavelength variation of <0.01 nm. The laser structure is simple and cost-effective.

Broadly Tunable SOA-Based Active Mode-Locked Fibre Ring Laser by Forward Injection Optical Pulse

We present a broadly tunable active mode-locked fibre ring laser based on a semiconductor optical amplifier (SOA), with forward injection optical pulses. The laser can generate pulse sequence with pulsewidth about 12ps and high output power up to 8.56dBm at 2.5 GHz stably. Incorporated with a wavelength-tunable optical bandpass filter, the pulse laser can operate with a broad wavelength tunable span up to 37nm with almost constant pulsewidth. A detailed experimental analysis is also carried out to investigate the relationship between the power of the internal cavity and the pulsewidth of the output pulse sequence. The experimental configuration of the pulse laser is very simple and easy to setup with no polarization-sensitive components.

A widely tunable dual-wavelength erbium-doped fiber ring laser operating in single longitudinal mode

A new mechanism to induce polarization hole burning effect in Er-doped fiber ring lasers is presented. By using this effect, incorporating with the counter-propagation of the two light beams, the inhomogeneous in the gain medium broadening was significantly increased, and thus a stable dual-frequency Er-doped fiber ring laser operating in single longitudinal mode and single-frequency was demonstrated. Frequency spacing was tunable from 0.47GHz to THz.

Continuously Tunable, Wavelength-Selective Buffering in Optical Packet Switching Networks

This letter investigates system performance of slow-light variable optical buffer based on cascaded stages of tunable silica microresonator rings. Continuous tunability is achieved by adjusting the resonance of each ring on the compact photonic integrated circuit. The all-pass configuration allows selectively applying variable delays to wavelengths of choice without losing any packets in an optical packet switching network.

High-Q active ring microwave resonators based on ferrite-ferroelectric layered structures

An electric and magnetic field tunable (dual-tunable) microwave active ring resonator is designed and characterized. The device structure is implemented with a microwave amplifier and a ferrite-ferroelectric delay line in the feedback loop. At 8GHz, an effective Q factor of 50 000 and tuning by 5MHz with an electric field are achieved. The performance characteristics of the resonator are presented and discussed.

Generation of doughnutlike vortex beam with tunable orbital angular momentum from lasers with controlled Hermite-Gaussian modes

This study demonstrates successive higher-order Hermite-Gaussian (HG(0,m)) mode operations in a microchip solid-state laser with a controlled off-axis laser diode (LD) pumping and generation of the corresponding doughnutlike laser beam of tunable ring diameter and orbital angular momentum, by experimentally focusing a Hermite-Gaussian mode (HGM) lasing beam into an astigmatic mode converter (AMC) with a mode-matching lens. Based on the successful generation of stable doughnutlike vortex beams by combining the LD off-axis pumping of microchip lasers and an AMC, this study proposes a design for a compact, solid doughnutlike vortex laser beam generator that combines three elements (i.e., laser cavity, mode-matching lens, and AMC) into one practical device. The desired doughnutlike vortex beam with different orbital angular momentum is easily generated by simply controlling the lateral off-axis pump position and pump beam shape on the laser crystal by numerical simulation.

Tunable ring laser based on a semiconductor optical amplifier at 1300 nm using a simple wavelength selection filter

A simple, compact, and low cost tunable ring laser with a commercial semiconductor optical amplifier (SOA) was demonstrated. The tunable ring laser is based on an external wavelength filter cavity that is analogous with the Littman configuration with a diffraction grating, a mirror, and a simple slit. The unique structural advantage of this new system is that the slit is displaced to select a desired wavelength instead of tilting the mirror as in the Littman configuration. This allows easy control over the selected wavelength by the translating action of the slit. The full width half maximum (FWHM) wavelength turning range is 45 nm, and the wavelength resolution is about 2 pm. The demonstrated tunable ring laser has 2 mW output power. The side mode suppression ratios is 70-73 dB.

Tunable multiwavelength fiber laser using a comb filter based on erbium-ytterbium co-doped polarization maintaining fiber loop mirror

A tunable comb filter based on a fiber loop mirror setup, which incorporates a piece of pumped erbium-ytterbium co-doped polarization maintaining fiber, is newly presented. It is accomplished by controlling the pump power or adjusting a polarization controller in the loop mirror, which results from the fact that the effective birefringence of the erbium-ytterbium co-doped polarization maintaining fiber depends on the pump power and polarization state of the traversing signal. By using the proposed comb filter, a continuously tunable multiwavelength fiber ring laser in the L-band is successfully demonstrated.

Discretely tunable and multiwavelength erbium doped fibre lasers with Fabry-Perot etalon

AbstractModern WDM telecommunication systems require stable and calibrated laser sources. In this paper, we present examples of such lasers based on erbium doped fibres, i.e., discretely tunable and multiwavelength ring lasers. For the first case, tuning is possible due to a tunable Bragg grating overlapping spectrally the third telecommunication window (1550 nm). When a Fabry-Perot etalon is inserted into the cavity, discrete tunable operation with appropriate spacing between operating wavelengths is possible. Different free spectral ranges (FSR) of applied etalons ensured operation at a wavelength spacing 0.4 nm, 0.8 nm or 1.6 nm, respectively. When an acoustooptical Bragg frequency shifter was inserted together with the Fabry-Perot etalon, the stable simultaneous multiwavelength operation covering the erbium doped gain range was achieved.