Monolithic Resonator Research Articles

A coplanar waveguide InAlAs/InGaAs HBT monolithic Ku-band VCO

An 18 GHz coplanar waveguide (CPW) monolithic voltage controlled oscillator (VCO) has been demonstrated using InAlAs/InGaAs HBT technology. The VCO achieves 6% frequency tuning range using a varactor diode constructed from the HBT base-emitter junction. A CPW design was employed to increase the Q-factor of the monolithic resonator as well as reduce the chip size. The VCO obtains an output power of +10/spl plusmn/0.5 dBm over the tuning range and a collector efficiency of 11.5%. A SSB phase noise of -72 and -96 dBc/Hz at 100 kHz and 1 MHz offset frequency from the carrier were achieved, respectively. This represents the first reported phase noise results of an InAlAs/InGaAs-based HBT VCO with a monolithic integrated varactor and are comparable to other MMIC HBT varactor-tuned VCO's reported in this frequency band.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

5 W, diffraction-limited, tapered-stripeunstable resonator semiconductor laser

A monolithic tapered-stripe unstable resonator laser diode operating at 952 nm wavelength is demonstrated to emit greater than 5.0 W in a diffraction-limited radiation pattern under pulsed conditions.

82% Efficient continuous-wave frequency doubling of 106 μm with a monolithic MgO:LiNbO_3 resonator

We describe a frequency-doubling monolithic standing-wave resonator made of MgO:LiNbO(3) with dielectric mirror coatings for impedance matching near 100 mW input power and near-optimum nonlinear coupling. An external conversion efficiency of 82% has been achieved.

Blue light generation by resonator-enhanced frequency doubling of an extended-cavity diode laser

Frequency doubling of diode laser radiation was achieved by operating an AR-coated diode laser in an extended laser cavity which contained a monolithic potassium niobate frequency doubling resonator as an intracavity element. Extended cavity operation ensured that the diode laser would oscillate only at frequencies that were resonant with the intracavity resonator. A diffraction grating was used to ensure single mode oscillation at the wavelength needed for noncritically phase-matched second harmonic generation. At 100 mA of injection current to the GaAlAs diode laser, 14 mW of 429 nm light were produced.

Compact source of coherent blue light

Generation of 22 mW of narrow-band radiation near 430 nm was achieved by frequency doubling the 100-mW output of a single-mode GaAIAs diode laser near 860 nm. A monolithic potassium niobate ring resonator serves as the nonlinear medium and at the same time as a reference cavity for the diode-laser frequency, which optically self-locks to a cavity resonance frequency. Continuous scans of the second-harmonic frequency over 330 MHz are achieved with the electro-optic effect. The results demonstrate a portable, economical, and efficient source of coherent blue light.

Fast amplitude modulation of the blue 429-nm output from a frequency-doubled GaAlAs diode laser

We report on a new method for fast amplitude modulation of blue 429-nm radiation that is produced by frequency doubling of a GaAlAs diode laser in a monolithic KNbO3 resonator. The diode-laser frequency was locked to the resonator by use of the Pound–Drever technique and FM sidebands that were generated by superimposition of an rf current on the diode-laser injection current. We modulated the blue power output by controlling the amplitude of this rf current, which controls the FM spectrum of the diode laser and thus the fraction of the diode-laser power that is coupled to the frequency-doubling resonator. Using this technique, we have produced blue pulses of 40-mW peak power with rise and fall times of 5 ns and pulse durations as short as 10 ns. Nonperiodic pulse sequences produced with this technique were used to write data on magneto-optical disks.

Nonlinear mode coupling in doubly resonant frequency doublers

The concept of a doubly resonant frequency doubler can be used for a variety of experiments concerning both classical phenomena like efficient frequency doubling at low power levels and quantum effects like squeezed states of light or Quantum Non Demolition (QND) measurements. In many of these experiments the strength of the nonlinear coupling of fundamental and second-harmonic modes is of crucial importance. First we treat the general theory for the calculation of the coupling parameterκ, which depends not only on properties of the nonlinear material but also on resonator geometry and some optical phases. On this basis we discuss in detail the situation for two different monolithic resonator geometries, namely a linear (standing-wave) and a ring (travelling-wave) cavity. Finally we compare theoretical predictions for these resonators to the experimentally achieved results.

High-power spatially coherent operation of unstable resonator semiconductor lasers with regrown lens trains

We have obtained high-power spatially coherent operation in wide-stripe InGaAs/GaAs/AlGaAs semiconductor lasers using a monolithic unstable resonator [consisting of diverging lens elements incorporated above an asymmetric graded-index separate confinement heterostructure (AGRIN-SCH)]. The fabrication involves MOCVD regrowth after wet-chemical etching of lens-like patterns in a GaAs layer above the active region. Pulsed output powers of 175 and 490 mW have been obtained in 170- and 100-μm-wide lasers, respectively, with spatial coherence in the near field exceeding 60%. We observe good lateral mode discrimination up to 3.5 times threshold in the 100-μm stripes with a round-trip magnification of 6.4.

Squeezing by second-harmonic generation in a monolithic resonator

We have measured the intensity fluctuations of the second-harmonic mode generated in a MgO:LiNbO3 external monolithic cavity pumped by a Nd:YAG laser. The cavity has mirror coatings for both the fundamental and the second-harmonic mode. We scan the cavity using the electro-optic effect of the crystal and observe that the second-harmonic beam of 2 mW exhibits a quantum noise reduction of 40(±5)%. In addition, we report on the active frequency stabilization of the monolithic device used in our squeezing experiments. Several fast tuning parameters such as the electro-optic effect, the photo-elastic effect, and the laser frequency have been investigated. With these tuning parameters the monolithic resonator can be locked on double-resonance at the phase-matching temperature, which is a prerequisit for observing squeezing in a cw-regime.

Monolithic resonator for a vibrating beam accelerometer

First Page

Efficient generation of blue light by doubly resonant sum-frequency mixing in a monolithic KTP resonator

Efficient generation of blue light is demonstrated by using resonantly enhanced sum-frequency mixing in a monolithic KTP resonator. Two infrared sources, a diode-pumped Nd:YAG laser and a GaAlAs laser diode, were simultaneously coupled into the monolithic cavity and tuned to resonant frequencies, so that high-intensity intracavity fields were built up at both wavelengths. A blue power of 4 mW in a TEM(00) mode was generated with 55% of the 30 mW of 809-nm power and 45% of the 33 mW of 1064-nm power coupled into the standing-wave nonlinear resonator. By using a novel monolithic ring resonator, 2 mW of power was generated in a TEM(00) mode at 462 nm. Electric-field-induced tuning of the resonant frequencies was also demonstrated.

Efficient diode-laser-pumped 946 nm Nd:YAG laser with resonator-enhanced pump absorption

The pump absorption of a 946-nm Nd:YAG laser was improved by resonating the GaAlAs diode-laser pump light in the 0.33-mm-long, monolithic laser resonator, whose maximum single pass pump absorption was only 18%. When the diode laser frequency was tuned to the pump resonance that was properly impedance matched, the Nd:YAG laser produced 29 mW from an incident diode laser power of 61 mW, for an overall efficiency of 48%. Laser oscillation was observed at both 946 nm and 938 nm. >

Fused-silica monolithic total-internal-reflection resonator

We have characterized a miniature fused-silica monolithic optical ring resonator in which the Gaussian mode is confined by total internal reflection. Laser light is coupled into and out of the resonator by frustrating one of the total internal reflections by means of a prism. The resonator can be overcoupled and undercoupled by varying the resonator–prism distance. The minimum measured resonator linewidth was less than 3 MHz. This type of broadband, stable, low-loss resonator has applications in linear and nonlinear optics.

Blue Laser Devices Using Frequency-Doubled Laser Diodes.

Modulatable, stable, and highly efficient small-size blue laser sources are recently considered very promising for high-density optical data storage, laser printer, and so on. A frequency-dou-bled AlGaAs laser diode using a monolithic KNbO3 resonator is expected to be more practical be-cause of its high SH power. We developed compact blue laser devices by this method. These devices, with size of 50×30×20mm3, have an SH output above 10mW with relative intensity noise of - 136dB/Hz and slightly elliptical Gaussian beam profile. We also found a new techni-que for direct modulation of blue radiation by using the EO-effect of KNbO3 crystal.

Efficient second-harmonic conversion of cw single-frequency Nd:YAG laser light by frequency locking to a monolithic ring frequency doubler

Efficient second-harmonic conversion of the 1064-nm output of a diode-pumped cw single-frequency Nd:YAG laser to 532 nm was obtained by frequency locking the laser to a monolithic ring resonator constructed of magnesium-oxide-doped lithium niobate. The conversion efficiency from the fundamental to the second harmonic was 65%. Two hundred milliwatts of cw single-frequency 532-nm light were produced from 310 mW of power of 1064-nm light. This represents a conversion efficiency of 20% from the 1-W diode laser used to pump the Nd:YAG laser to single-frequency 532-nm output. No signs of degradation of the 532-nm power or photo-refractive damage in the crystal were observed for over 500 h of operation of the system at green output powers greater than 100 mW.

High-power single-mode diode-pumped Nd:YAG laser using a monolithic nonplanar ring resonator

A 0.91-W single-frequency diode-pumped Nd:YAG laser at 1.06 microm is demonstrated with a TEM(00) output. We also report a 60% slope efficiency from another nonplanar monolithic ring laser with diffraction-limited, single-frequency, 1.06-microm output. Injection locking of two 0.17-W monolithic nonplanar ring resonators gave 0.34 W of single-mode power. Actively controlled injection locking of two lasers was demonstrated for indefinite periods.

Generation of 41 mW of blue radiation by frequency doubling of a GaAlAs diode laser

A monolithic ring resonator of KNbO3 was used for efficient frequency doubling of a 856 nm GaAlAs diode laser. A special electronic servo technique was devised to lock the diode laser frequency to the KNbO3 cavity so that stable generation of blue output was obtained. With 105 mW of incident near-infrared power, 41 mW of 428 nm radiation were produced. The conversion efficiency from electrical input power into the diode laser to blue output was ∼10%.

Monolithic IMPATT oscillator characterization

Two methods were developed to characterize the monolithic IMPATT resonator used in the design of the millimeter-wave oscillators. Although they are only good for discrete frequency points, the accuracy is much better than the method of de-embedding. The transmission resonance method can also be applied to other circuitry with high reflection coefficients, such as the matching circuit of a narrowband power FET, or HBT. The varactor method is very handy for in situ measurements. The drawback is that it is destructive and the accuracy deteriorates when the loss is high (a small arc). The experimental results are valuable for monolithic IMPATT oscillator design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Confocal unstable-resonator semiconductor laser

GaAs/GaAlAs heterostructure lasers with a monolithic confocal unstable resonator were demonstrated. The curved mirrors satisfying the confocal condition were fabricated by etching. Close to threshold, the lasers operate in a single lateral mode with a nearly collimated output beam. A single-lobe far-field intensity distribution as narrow as 1.9 degrees full width at half maximum was measured.

A guided wave monolithic resonator ruby fiber laser

Single crystal ruby fibers, cooled with liquid nitrogen, have been operated as end pumped lasers. The fiber laser is a guided wave device with a length of 15 mm and a mean diameter of 60 μm. The laser resonator structure is monolithic, consisting of an aluminium mirror coated on one fiber end face and an uncoated opposite end face serving as an output coupler. Using an argon ion laser pump source, cw output powers of several mW were obtained.