Output Power Of Laser Diode Research Articles

Efficient Light Coupling and Propagation in Fiber Optic Systems

This study explores the propagation of light in optical fibers, focusing on the fundamental principles and practical implications for fiber optic technologies. By analyzing the wave equation, the research demonstrates that light propagates as cylindrical waves within the fiber, contrasting with spherical waves in free space. The study highlights the significance of Gaussian beams, particularly from helium-neon lasers, finding a beam waist radius of approximately 12.6 μm and its position about 1.25 μm from the focus. These parameters are critical for optimizing laser beam coupling into the fiber. The research also measures the light transit time through a 100-meter fiber, revealing a light speed of approximately 2×108 m/sec, which is influenced by the fiber's refractive index. Additionally, the relationship between diode laser output power and injection current was investigated, demonstrating a linear correlation crucial for practical applications. The findings emphasize the importance of accurate measurements and configuration in improving fiber optic communication and laser performance. This comprehensive analysis provides valuable insights into the design and optimization of optical fiber systems, contributing to advancements in communication and laser technologies.

Microcontroller-Based Thermoelectrically Stabilized Laser Diode System

This work aims to describe the development of a prototype laser diode system along with its driver circuit and a stable microcontroller-based thermo-electric cooling system. The laser diode driver circuit was designed and simulated by using NI Multisim. The driver circuit was built using two LM317 ICs to control the voltage across the laser diode and current through the laser diode. The laser diode output power varies by varying the current across the laser diode through the driver circuit. The temperature of the laser diode rises with time, affecting the output power of the laser diode during a long period of operation. A microcontroller-based cooling system was designed and fabricated using thermoelectric coolers. The microcontroller controls the cooling system ON/OFF period to maintain the laser diode at a particular temperature by removing the excess heat produced during the lasing action. The laser diode with a microcontroller-based cooling system shows that the laser diode output power remains stable during a long period of operation.

Sagnac with Double-Sense Twisted Low-Birefringence Standard Fiber as Vibration Sensor.

In this work, we study a double-sense twisted low-birefringence Sagnac loop structure as a sound/vibration sensing device. We study the relation between the adjustments of a wave retarder inside the loop (which allows controlling the transmission characteristic to deliver 10, 100, and 300 μW average power at the output of the system) and the response of the Sagnac sensor to vibration frequencies ranging from 0 to 22 kHz. For a 300 m loop Sagnac, two sets of experiments were carried out, playing at the same time all the sound frequencies mixed for ∼1 s, and playing a sweep of frequencies for 30 s. In both cases, the time- and frequency-domain transmission amplitudes are larger for an average power of 10 μW, and smaller for an average power of 300 μW. For mixed frequencies, the Fourier analysis shows that the Sagnac response is larger for low frequencies (from 0 to ∼5 kHz) than for high frequencies (from ∼5 kHz to ∼22 kHz). For a sweep of frequencies, the results reveal that the interferometer perceives all frequencies. However, beyond ∼2.5 kHz, harmonics are present each ∼50 Hz, revealing that some resonances are present. The results about the influence of the power transmission through the polarizer and power emission of laser diode (LD) on the Sagnac interferometer response at high frequencies reveal that our system is robust, and the results are highly reproducible, and harmonics do not depend on the state of polarization at the input of the Sagnac interferometer. Furthermore, increasing the LD output power from 5 mW to 67.5 mW allows us to eliminate noisy signals at the system output. in our setup, the minimum sound level detected was 56 dB. On the other hand, the experimental results of a 10 m loop OFSI reveal that the response at low frequencies (1.5 kHz to 5 kHz) is minor compared with the 300 m loop OFSI. However, the response at high frequencies is low but still enables the detection of these frequencies, yielding the possibility of tuning the response of the vibration sensor by varying the length of the Sagnac loop.

Penstabilan Daya Dioda Laser Secara Otomatis Sebagai Sumber Cahaya Pada Sensor Optik

Since the invention of laser beam in the 1960s, the application extends to all areas, even revolutionizedseveral fields of technology. Laser is the most widely used in electronic applications as the laser diode. Theimportant application of laser diodes is as a light source for an optical sensor on the sensor either directly orusing the optical fiber. In the application as light source in optical sensor applications, especially on the principleof change in intensity, the stability of laser diode output power is a variable that should be received the necessaryattention. So that, it is needed a Power Control which will automatically control the output power of laser beam.In this study we designed the power stability circuits using the APC LD 2000. The measurement results show thatthe stability strongly depended on the injection electric current area. When it was be operated in the largerinjection electric current area, the laser diode power tobecame larger and more stable than using with themedium or the lower injection electric current.

Improving Output Power of InGaN Laser Diode Using Asymmetric In0.15Ga0.85N/In0.02Ga0.98N Multiple Quantum Wells.

Herein, the optical field distribution and electrical property improvements of the InGaN laser diode with an emission wavelength around 416 nm are theoretically investigated by adjusting the relative thickness of the first or last barrier layer in the three In0.15Ga0.85N/In0.02Ga0.98N quantum wells, which is achieved with the simulation program Crosslight. It was found that the thickness of the first or last InGaN barrier has strong effects on the threshold currents and output powers of the laser diodes. The optimal thickness of the first quantum barrier layer (FQB) and last quantum barrier layer (LQB) were found to be 225 nm and 300 nm, respectively. The thickness of LQB layer predominantly affects the output power compared to that of the FQB layer, and the highest output power achieved 3.87 times that of the reference structure (symmetric quantum well), which is attributed to reduced optical absorption loss as well as the reduced vertical electron leakage current leaking from the quantum wells to the p-type region. Our result proves that an appropriate LQB layer thickness is advantageous for achieving low threshold current and high output power lasers.

Combined dual-wavelength laser diode beam end-pumped single longitudinal mode Pr<sup>3+</sup>:LiYF<sub>4</sub> 360 nm ultraviolet laser

In recent years, all-solid-state ultraviolet lasers have had widely potential applications in the fields of spectroscopy, biological analysis, precision manufacturing, optical data storage, high-resolution printing, medicine and lithography. The good monochrome of all-solid-state ultraviolet laser can improve the accuracy of spectral absorption measurement when used to detect specific proteins and reduce the laser spot diameter when used for high density data storage or acousto-optic deflector. In this paper, a combined dual-wavelength laser diode (LD) beam end-pumped single longitudinal mode Pr<sup>3+</sup>:LiYF<sub>4</sub> all-solid-state UV laser at 360 nm is presented. A V-folded cavity structure is used in the laser, which consists of a reflective volume Bragg grating (RBG) and a Fabry-Perot (F-P) etalon. The RBG is used as a wavelength selection and resonator reflector to narrow the width of spectral line. The F-P etalon is hybrid in the cavity, serving as a narrow-band filter, to achieve the single longitudinal mode. The lithium triborate crystal with critical type-I phase matching at room temperature is used for implementing the second-harmonic generation of the fundamental 720 nm laser and obtaining an efficient and compact ultraviolet laser at 360 nm. The optical resonator is simulated and analyzed by MATLAB software. Two experiments are conducted to compare the accuracy of central wavelength tuning by changing the temperature of F-P etalon and the angle of F-P etalon. The result shows that the change temperature of F-P etalon can achieve 0.165 pm/℃, showing that it is a better method. The structure of the laser is simplified and the anti-interference capability is improved in this way. It is different from mode competition method and the stability of single longitudinal mode laser output is increased. When the output power of LD at 444 nm is 1200 mW and that of LD at 469 nm is 1400 mW, a single longitudinal mode CW UV laser at 360 nm with output power as high as 112 mW is achieved. The optical-to-optical conversion efficiency is 4.3%, and the longitudinal linewidth of laser is 30 MHz. The measurements show that the edge suppression ratio is greater than 60 dB, the stability of root mean square (RMS) of output power in 4 h is better than 0.5%, the frequency shift in 1h is better than 220 MHz, and amplitude noise is less than 0.5%.

Suppression of electron and hole overflow in GaN-based near-ultraviolet laser diodes* *Project supported by the Science Challenge Project, China (Grant No. Z2016003), the National Key R & D Program of China (Grant Nos. 2016YFB0400803 and 2016YFB0401801), the National Natural Science Foundation of China (Grant Nos. 61674138, 61674139, 61604145, 61574135, 61574134, 61474142, 61474110, 61377020, and 61376089), and the Beijing Municipal Science

In order to suppress the electron leakage to p-type region of near-ultraviolet GaN/In x Ga1–x N/GaN multiple-quantumwell (MQW) laser diode (LD), the Al composition of inserted p-type Al x Ga1–x N electron blocking layer (EBL) is optimized in an effective way, but which could only partially enhance the performance of LD. Here, due to the relatively shallow GaN/In0.04Ga0.96N/GaN quantum well, the hole leakage to n-type region is considered in the ultraviolet LD. To reduce the hole leakage, a 10-nm n-type Al x Ga1–x N hole blocking layer (HBL) is inserted between n-type waveguide and the first quantum barrier, and the effect of Al composition of Al x Ga1–x N HBL on LD performance is studied. Numerical simulations by the LASTIP reveal that when an appropriate Al composition of Al x Ga1–x N HBL is chosen, both electron leakage and hole leakage can be reduced dramatically, leading to a lower threshold current and higher output power of LD.

Suppression the Leakage of Optical Field and Carriers in GaN-based Laser Diodes by using InGaN Barrier Layers

GaN-based laser diodes (LDs) with different barrier layers are investigated by using simulation and experimental methods. it is found that the absorption loss always decreases with the increasing indium content of the InGaN barrier layer in InGaN/InGaN multiquantum well (MQW) LDs, It leads to an increase of slope efficiency and output power of LDs due to the better optical confinement effect of laser beam. However, when the barrier layer changes from InGaN to AlGaN, both threshold current and slope efficiency deteriorate seriously. Except for the increase of the optical absorption loss resulting from the leakage of the optical field, a large leakage of carriers due to the increased piezoelectric polarization field in InGaN/AlGaN MQW region may also be responsible for this deterioration. Therefore, suppressing the leakage of the optical field and carriers by using relatively higher In content InGaN barrier layer is benefit for obtaining high-performance LDs with low threshold current and high output power.

Suppression of hole leakage by adding a hole blocking layer prior to the first quantum barrier in GaN‐based near‐ultraviolet laser diodes

Compared with GaN‐based visible GaN/InGaN multiple‐quantum‐well laser diodes (LDs), near‐ultraviolet LDs may suffer from a sever hole leakage due to the shallower quantum wells (QWs). Here, a 10 nm n‐type AlGaN hole blocking layer (HBL) is proposed to put before the first quantum barrier layer and form a barrier on the valence band to prevent injected holes from leaking into the n‐type region. Furthermore, the effect of Al composition of AlxGa1−xN HBL on LD performance is studied. Theoretical analysis is performed by using advanced device simulation. The simulation results show that lower threshold current and higher output power of LD can be obtained when Al composition of AlxGa1−xN HBL is 0.23. This result can be attributed to a dramatically reduced electron and hole leakage, and more stimulated recombination in QWs.

Doping effects in p- and n-type layers of 390-nm InGaN DQW lasers

The performance characteristics of deep violet InGaN laser diodes (LDs) are theoretically studied with the effects of doping concentrations in p- and n-type layers. Comprehensive study on output performance characteristics such as output power, threshold current, slope efficiency, DQE, and optical intensity, as well as on several internal parameters such as quantum well (QW) carrier densities, electron and hole current densities of deep violet InGaN double quantum well (DQW) lasers, have been done. The simulation results indicate that output power of LD is increased by increasing doping concentration in both n- and p-type layers. it can be due to increased carrier current densities and consequently increased radiative recombination. The results also indicate decrease in slope efficiency and DQE with increasing doping concentration. This situation can be caused by increasing nonradiative recombinations, such as Auger recombination inside and outside the active region, current overflow from the active region, and optical losses. Increasing current overflow from the active region also causes an increase in threshold current. Using higher doping concentration in n-type layers results in increase in electron current density in the n-side and consequently, higher electron flow in the active region. It causes an increase in higher radiative recombination and a higher need for holes and consequently, a higher hole current density in p-type layers. As well as, optical intensity of LDs is increased by increasing the doping concentration.

带前置光放大的星间微波光子链路建模及性能优化

An optical preamplifier is applied to increase the signal-to-noise ratio (SNR) of inter-satellite microwave photonics links considering the large signal loss in distant propagation. An optically preamplified intersatellite microwave photonics links model is established and an analytical expression of SNR is derived with the method of expanding Bessel series and Graf addition theorem. The dominant noise components influence the link performance is confirmed, given the desired SNR, the direct current (DC) bias phase shift of modulator can be optimized so as to minimize the output power of laser diode (LD) under different gain of optical preamplifier, and the effects of the optical preamplifier gain on the minimum output power of LD and optimal DC bias phase shift is also examined. According to the numerical results, the output power of LD needed to achieve the required SNR decreases while increasing the gain of preamplifier, and the corresponding optimal DC bias phase shift decreases first and then increases. For QPSK modulation signal, the output power of LD needed to achieve the SNR of 15.56 dB (BER=10-9) is at least 45 dBm without an optical preamplifier, while the output power of LD is required only 22.57 dBm as the gain of preamplifier is 15 dB.

Experimental research on profile measurement based on laser optical feedback

A novel method of profile measurement for reflective surface based on optical feedback is proposed in this paper. With so-called self-mixing structure, a fraction of the light emitted from a laser diode (LD) is reflected back by the target under test and returns the laser cavity and changes the operation mode of this LD. When the laser operates in coherence collapse regime, the output power of LD is affected by the optical feedback coefficient, while the coefficient is decided by the defocusing amount and the reflectivity of the target under test. Therefore, through scanning coins three-dimensionally and measuring the output power of LD, we obtain the profile information of samples. Compared with the conventional interferometry, this technique is advantageous of accuracy, compactness and low cost.

Optimization of the cavity facet coating in high power GaN-based semiconductor laser diodes

A method to calculate the reflectivity of the coated cavity facet was proposed, and the distribution of the optical power near the two coated cavity facets was calculated for GaN-based laser diodes. A new design method for reducing the optical power at the two cavity facets without changing the output power of laser diodes was discussed, which is helpful to optimize the cavity facet coating and raise the threshold current at which catastrophic optical damage occurs.

Lateral power-monitoring photodiode monolithically integrated into 1.3 μm GaInAsP laser

This study describes a method to produce a novel Lateral-side Power-Monitoring Photodiode (Lateral PMD) and a ridge stripe waveguide Laser Diode (LD) integrated into a monolithic structure using conventional laser process technology. Compared with the LDs of traditional monolithically integrated Rear-side Power-Monitoring Photodiodes (Rear PMDs), the cleaved facets in the new structural LDs remain undamaged, and therefore have a lower threshold current (28 mA) and red-shift rate (0.31 nm/°C) and higher slope efficiency (11.93%). In addition, the characteristics are close to those of a conventional LD. Furthermore, under −0.2 V, the Lateral PMD still provides high linear monitoring capabilities for an LD with a light output power of 8.33 mW. Even after long periods of operation, the variations in LD output power and Lateral PMD photocurrent both fall within a range of 1%. This indicates that a monolithically integrated Lateral PMD is extremely reliable.

Theoretical and experimental investigations of the limits to the maximum output power of laser diodes

The factors that limit both the continuous wave (CW) and the pulsed output power of broad-area laser diodes driven at very high currents are investigated theoretically and experimentally. The decrease in the gain due to self-heating under CW operation and spectral holeburning under pulsed operation, as well as heterobarrier carrier leakage and longitudinal spatial holeburning, are the dominant mechanisms limiting the maximum achievable output power.

High stable power control of a laser diode

In this paper, the low and the high frequency noises of a laser diode have been analyzed. Based on the analysis a novel scheme that adapts analog and digital hybrid techniques is proposed to stabilize the output power of a laser diode. With the hybrid controller, the low and the high frequency noises of a laser diode are conspicuously reduced. By accurate calculation, the short-term stability of the output power of laser diode reaches ±0.55‰, and the long-term stability is ±0.7‰.

Thermal properties of diamond/copper composite material

Thermal considerations are becoming increasingly important for the reliabilities of the electronics parts as the electronics technologies make continuous progress such as the higher output power of laser diodes or the higher level of integration of ICs. For this reason the desire for improving thermal properties of materials for electronics component parts is getting stronger and the material performance has become a critical design consideration for packages. To meet the demands for a high performance material for heat spreader materials and packages, a new composite material composed of diamond and copper was successfully manufactured under high pressure and high temperature. The effects of diamond particle sizes and the volume fractions of diamond on both thermal conductivity and the coefficient of thermal expansion (CTE) were investigated. The thermal conductivity of the composite material was dependent on both the particle size and the volume fraction of diamond, while the CTE was dependent only on the volume fraction of diamond. At the higher diamond volume fraction, the experimentally obtained thermal conductivities of the composite materials were above the theoretically expected values and the experimentally obtained CTE were between the two theoretical Kerner lines. This may be due to the fact that at the higher diamond volume fraction the diamond particles are closely packed to form bondings between each particle. The composite of diamond and copper have a potential for a heat spreading substrate with high performance and high reliability because not only its thermal conductivity is high but its coefficient of thermal expansion can be tailored according to a semiconductor material of electronics devices.

Optical generation of millimeter and submillimeter-waves through optical side-band injection locking of semiconductor lasers

In this letter, we propose a novel scheme for realizing a tunable source of millimeter (mm)- and submillimeter (submm)-waves by mixing two coherent lightwaves in a wide-band photodiode. The coherent lightwaves are generated from two laser diodes injection locked to two optical side-bands generated from a overdriven phase modulator. Calculated submm-wave power at a frequency of 200 GHz generated by this method is 1.2 mW for each laser diode output power of 20 mW. The proposed method possesses a unique advantage of phase noise reduction of the generated mm-wave.

Observation of a Fringe Locking Phenomenon in a Self-Feedback Laser Diode Interferometer

A fringe locking phenomenon in a two beam-laser diode interferometer with optical feedback is observed. If a fraction of at least 0.1% of the laser diode output power is returned to it, the fringes are locked even in the presence of the vibrations of an interferometer mirror with an amplitude of two wavelengths and this locking can also be maintained for mirror displacements over 20 mm. Dependence of the fringe phase fluctuation on the frequency of vibration and the optical path differences of the interferometer are experimentally studied. A theoretical model based on the equivalent Fabry-Perot cavity for the laser diode interferometer is proposed and shows good agreement with experimental results.

Ultra-wideband source using gallium arsenide photoconductive semiconductor switches

An ultrawide-band (UWB) pulse generator based on high-gain (lock-on mode) gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) is presented. Revised PCSS contact design shows improved performance in hold-off field, on-state switch potential, and switching jitter, while reducing the switch volume by 75% compared to previous designs. A compact laser diode module operates at 904 nm and triggers the PCSS at pulse repetition rates (PRR) of up to 2 kHz. The 625 W laser diode output power is found to be sufficient to produce switching jitter of 65 ps rms at a switched field of 80 kV/cm. The PCSS switching jitter is found to have a strong dependence upon the switched field when triggered with the laser diode module. The revised PCSS geometry is easily integrated into a compact, parallel-plate source used to drive a TEM horn impulse-radiating antenna. The radiated field has a rise time of 330 ps and an adjustable low-frequency spectrum.