Wavelength Tunable Laser Diode Research Articles

Long external cavity Si photonic wavelength tunable laser diode

We fabricated wavelength-tunable laser diodes with external cavity consist of Si photonic wire waveguide ring resonators. About 51.5 nm wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. The cavity length dependence of the spectral line width was verified to obtain narrower spectral linewidth. The observed spectral linewidth of 3.78 mm long cavity and 8.19 mm long cavity are 131.0 and 64.8 kHz, respectively. The advantage of long external cavity to design the narrow spectral linewidth Si photonic wavelength tunable laser diode was confirmed.

25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity

We report on the spectral properties of a diode laser with a tunable external cavity mirror, realized as an integrated optics waveguide circuit. Even though the external cavity is short compared to that of other narrow bandwidth external cavity lasers, the spectral bandwidth of this tunable laser is as small as 25 kHz (FWHM). The side-mode suppression ratio (SMSR) is 50 dB. The laser is able to access preset wavelengths in 200 μs and can be tuned over the full telecommunications C-band (1530–1565 nm).

All-optical analog-to-digital conversion scheme based on Sagnac loop and balanced receivers

An all-optical analog-to-digital conversion scheme based on a Sagnac loop and balanced receivers is proposed and experimentally demonstrated. Adjustable phase shift about the transfer function of the Sagnac loop is obtained by using the multiwavelength optical pulses to realize the phase-shift optical quantization. Benefit from the complementary outputs at the transmitted and reflected ports of the Sagnac loop and balanced receiver can be used to obtain the quantized output binary signal for the encoding operation. A proof-of-concept experiment is implemented using a wavelength tunable continuous-wave laser diode. Using 16 different wavelengths, the 16 quantization levels are demonstrated and an effective number of bits (ENOB) of 4 bits is obtained.

All-Optical Analog-to-Digital Conversion Using Inherent Multiwavelength Phase Shift in LiNbO$_{3}$ Phase Modulator

All-optical analog-to-digital conversion utilizing inherent multiwavelength phase shift in lithium niobate phase modulator is proposed. In the experimental demonstration, a wavelength-tunable continuous-wave laser diode and a lithium niobate phase modulator are used to quantize the sinusoidal tone electrical analog signal. Using 16 different wavelengths, an effective number of bits of 4.3-bit has been obtained after software sampling measurement. Benefits of the presented approach in this letter are its simple realization of the phase shift and high stability.

A Simplified Fabry–PÉrot Electrooptic-Modulation Sensor

A simplified electrooptic (EO)-sensing system that employs a wavelength-tunable laser diode and an EO-crystal microcavity is presented. A theoretical model simulating a Fabry-Perot-based Pockels-effect probe demonstrates that both the EO phase retardation and modulation-efficiency slope of the optical system can be resonantly enhanced. Consequently, it predicts that electric-field measurements are possible using a configuration that eliminates the polarizer, analyzer, and quarter-wave retarder of typical EO intensity modulators. An experimental verification of the concept is presented using thin, uncoated, LiTaO crystals, and an EO modulation signal that is 60 dB above the system noise floor obtained.

Improvement in Temperature Tolerance of Holographic Data Storage Using Wavelength Tunable Laser

In this paper, we report a new method of increasing the temperature tolerance of holographic recording media using a wavelength tunable laser. Of all holographic media, photopolymer media are particularly sensitive to temperature, thus some methods are required to maintain a low bit-error ratio (BER) as temperature changes. We demonstrate here how to maintain a high signal-to-noise ratio (SNR) as temperature changes using a wavelength tunable blue external cavity laser diode (ECLD) currently under development. For comparison, we analyze the temperature tolerance by a angle-tuning method and a wavelength-tuning method. We have focused that a hybrid of wavelength-tuning and angle-tuning method, we can read out the full of the image at 60°C, which is +30°C above the recording temperature. Moreover, we propose a recording method that allows the wavelength to be adjusted to the temperature changes. By adjusting the wavelength linearly to the temperature changes during recording, we can read out the holograms recorded at different temperatures using the wavelength corresponding to the readout temperature.

Tunable blue laser based on intracavity frequency doubling with a fan-structured periodically poled LiTaO_3 crystal

We introduce a new concept for a wavelength-tunable frequency-doubled laser diode with a single control parameter. The concept is based on intracavity frequency doubling in an external resonator geometry with spatial separation of the spectral components. The use of a fan-structured periodically poled LiTaO(3) crystal permits tuning of both the fundamental and the second harmonic simultaneously with one aperture. We demonstrate tunability over more than 10 nm in the blue (480.4 to 490.6 nm) with output powers of the order of 50 nW.

Piezoelectric effects in semiconductor heterostructures: applications and consequences

The piezoelectric (PZ) effect in strained semiconductor heterostructures can be used as an additional degree of freedom in designing novel heterostructures with desired optoelectronic properties. After a short review of previous work in the field, we discuss two examples in which the presence of the PZ field is either beneficial or unwelcome. First, we present a wavelength-tunable laser diode whose tuning mechanism is based on the quantum confined Stark effect and we show that the tuning range of the device can be significantly enhanced if the active quantum well contains a PZ field. Next, we discuss the case of nitride heterostructures where unwanted polarization-induced electric fields limit seriously their performance in optoelectronic applications. We show that the use of quaternary nitrides can help circumvent this problem.

Integrated micromachined tunable lasers for all optical network (AON) applications

A miniaturized wavelength-tunable diode laser has been demonstrated in this paper for all optical network (AON) applications. Also, a medium feedback model has been developed to study the wavelength tuning characteristics of the micromachined tunable lasers. The miniaturized tunable laser with a size of 2 mm ×1.5 mm is formed by a Fabry–Perot (FP) diode laser, a surface micromachined mirror and a butt-coupled optical fiber that can give a wavelength tuning range of 16 nm.

Diode laser sensor for process control and environmental monitoring

Absorption spectroscopy with tunable diode lasers (TDLAS) in the infrared region is a well-known technique for the chemical analysis of gas mixtures. The laser provides a high selectivity, which is important in industrial environments such as in-line stack monitoring, where complex gas mixtures are present. A wavelength tunable diode laser in the near infrared region has been utilized as a light source in absorption measurements of air pollution resulting from energy usage for industry. The emission frequency can be varied over a relatively wide spectral range by changing the current and temperature of the diode.

Transduction mechanisms of the Fabry-Perot polymer film sensing concept for wideband ultrasound detection

The transduction mechanisms of a wideband (30 MHz) contact ultrasound sensor based upon the use of a thin polymer film acting as a Fabry-Perot interferometer have been investigated. Polyethylene terepthalate (PET) sensing elements, illuminated by the free-space collimated output of a wavelength-tunable DBR laser diode, have been used to study the sensor transfer function, sensitivity, the effect of water absorption, and frequency response characteristics. Acoustic performance was evaluated by comparing the sensor output with that of a calibrated PVDF membrane hydrophone using laser-generated acoustic transients as a source of broadband ultrasound. An ultrasonic acoustic phase sensitivity of 0.1 rad/MPa, a linear operating range to 5 MPa, and a noise-equivalent-pressure of 20 kPa over a 25 MHz measurement bandwidth were obtained using a water-backed 50 mum PET sensing film. A model of frequency response that incorporates the effect of an adhesive layer between the sensor film and backing material has been developed and validated for different sensing film thicknesses, backing configurations, and adhesive layer thicknesses.

High-density wavelength switching obtained from a tunable multisection laser diode

We describe a method based on multistability in wavelength for obtaining high-density wavelength switching for application to signal routing. The method relies on the use of a 1550-nm wavelength-tunable multielectrode laser diode that is fed back electrically. The system operates as a multistable device that exhibits multiple steady states in wavelength. The device can be used to convert time-multiplexed packets into wavelength-multiplexed signals.

Design and analysis of micromechanical tunable interferometers for WDM free-space optical interconnection

This paper proposes a new concept of high density chip-to-chip optical interconnection based on wavelength division multiplexing (WDM), which can be realized as a microelectromechanical system (MEMS) device. The output signals from a preprocessing integrated circuit (IC) chip (N channels) are converted to optical signals of different wavelengths by using wavelength tunable laser diodes and projected onto an array of wavelength-selective photodiodes. Channel connection is made by wavelength matching between the light sources and detectors, by using micromechanical Fabry-Perot interferometers. In this scheme arbitrary 1 to 1 connection as well as 1 to N or N to 1 connection is available. Since the input/output connections are made in an optical manner, the switching state can be reconfigured and the whole switching system can be integrated in a compact space. We have investigated design principle of the micromechanical Fabry-Perot interferometers for tunable photodiodes to maximize the switching contrast and channel density in a given wavelength range. The preliminary interferometer arrays are implemented by silicon-based surface micromachining.

Chaotic oscillator in wavelength: a new setup for investigating differential difference equations describing nonlinear dynamics

A generator of chaos in wavelength is reported. It is formed by a wavelength-tunable laser diode with a time delayed feedback loop in which a wavelength nonlinear-linear device is introduced. The dynamical regime of wavelength emission thus obtained is ruled by a differential difference equation. Experimental results are compared with numerical simulations and with previous theoretical and experimental results.

Chaos in wavelength with a feedback tunable laser diode

Wavelength is used to induce optical nonlinearities and to generate chaos from a multielectrode wavelength tunable laser diode. Chaotic modulation of wavelength ruled by a nonlinear differential difference equation is demonstrated. The method offers a high flexibility, which should open the way to simple chaotic systems with complicated nonlinear functions.

Wavelength-multiplexed holographic data storage by use of reflection geometry with a cerium-doped strontium barium niobate single-crystal structure and a tunable laser diode

We present wavelength-multiplexed holographic recording forhigh-density, high-speed data storage using reflection geometry with ahigh-sensitivity cerium-doped strontium barium niobate single-crystalstructure and second-harmonic generated light from a compact andconvenient wavelength-tunable laser diode. We have recorded andreconstructed wavelength-multiplexed holograms by using wavelengths0.053-nm apart. The theoretical wavelength selectivity of thehologram with the linewidth of the light source taken intoconsideration agrees well with the experimental wavelength selectivity.

Tunable twin-guide (DFB) laser with buried facetsfor reduced spectral linewidth broadening

The spectral linewidth of continuously wavelength tunable laser diodes has been significantly reduced by the buried facets technique. Embedding the λg = 1.3 µm InGaAsP tuning region of a λ = 1.55 µm tunable twin-guide distributed feedback laser entirely in high-bandgap InP suppresses the electronic 1/f noise by more than 10 dB, yielding a spectral linewidth up to a factor of two smaller during tuning.

Linewidth broadening by 1/f noise in wavelength-tunable laser diodes

The excess linewidth broadening of continuously tunable InGaAsP/InP laser diodes at 1.5 μm wavelength is investigated. Terminal electrical and FM noise measurements indicate that the recombination processes in the forward biased tuning region produce significant 1/f carrier noise. Below 1 MHz the 1/f noise dominates yielding a noise enhancement of about 30 dB at 1 kHz. The discrepancy observed so far between theoretically expected and measured spectral linewidth can be well resolved by taking into account this additional noise source.

Broadly tunable laser-diode-based mid-infrared source with up to 31 μW of power at 43-μm wavelength

High-power single-spatial-mode near-IR laser diodes are mixed in periodically poled LiNbO(3) (PPLN) to generate broadly tunable mid IR-radiation. Conversion efficiencies to the mid IR up to 0.017%/W are demonstrated, and up to 31 microW of power is generated at the spectroscopically important 4.3-microm wavelength. We achieved broadband mid-IR tunability by mixing a wavelength-tunable laser-diode pump source with a fixed-wavelength master oscillator power amplifier laser-diode signal source in a PPLN sample that has a poling period that varies from 21.0 to 22.6 microm in the direction transverse to the beam propagation. We generated mid-IR radiation from 4.1 to 4.3 microm with these laser sources, using a fixed 22.0-microm period region of the sample.

Broadly tunable mid-IR radiation source based ondifferencefrequency mixing of high power wavelength-tunable laserdiodes in bulk periodically poled LiNbO 3

Coherent mid-IR radiation throughout the 3.6 to 4.3 µm wavelength range is generated by difference frequency mixing (DFM) of wavelength-tunable laser diodes in periodically-poled LiNbO3 (PPLN). Mid-IR power levels up to 7.1 µW and DFM conversion efficiencies up to 0.015%/W cm are demonstrated.