InGaAsP Laser Diodes Research Articles

Modeling of 1300 nm hybrid III-V/silicon lasers

In this study, the modeling of a III–V-Si hybrid semiconductor laser with an InGaAsP 80 nm thick active layer at a wavelength of 1300 nm was carried out using the LaserMOD commercial software program. The mesh, gain, optical output power, optical spectrum, transient response, and near-field and far-field of the laser designed as a result of the simulations were analyzed. It was observed that the light generated in the multi quantum well (MQW) layer can be successfully transferred to the Si waveguide, allowing for light transfer from one point to another in the photonic integrated circuit (PIC) structure. From the L-I curve of the hybrid laser, the threshold current and spectral width were found to be 5 mA and 13 nm, respectively. These results were compared with those of the InGaAsP/InP laser which had a threshold current of 30 mA and spectral width of 36 nm. This demonstrates that the hybrid laser outperforms the InGaAsP diode laser by having a significantly lower threshold current and better spectral coherence. The material gain peaks and the center wavelength of the optical spectrum were obtained around 1305 nm (0.96 eV), which is consistent with the design target of the laser. Additionally, in the transient response of the hybrid laser, it was observed that the oscillations that occur at the rising and falling edges of the light output were damped after approximately 500 ps. Finally, near-field and far-field results demonstrate that a single mode operation was achieved from the hybrid laser.

High-power laser photobiomodulation therapy for immediate pain relief of refractory oral mucositis.

We aimed to evaluate the efficacy of high-power (class IV) laser photobiomodulation (PBM) therapy for immediate pain relief due to oral mucositis (OM) refractory to recommended first-line therapy. This retrospective study included 25 cancer patients with refractory chemotherapy- or radiotherapy-induced OM (16 and 9 patients, respectively) that were treated for pain relief with an intraoral InGaAsP diode laser (power density = 1.4 W/cm2). Pain was self-assessed immediately before and after laser treatment using a 0-to-10 numeric rating scale ([NRS], "0" = no pain, "10" = intolerable pain). Patients reported an immediate decrease in pain following 94% (74 of 79) of the PBM sessions, in 61% (48 sessions) the pain reduction was over 50%, and in 35% (28 sessions) the initial pain was completely eliminated. There were no reports of increased pain post-PBM. For chemotherapy and radiotherapy-treated patients, mean reduction in pain NRS post-PBM was 4.8 ± 2.5 (p < 0.001) and 4.5 ± 2.8 (p = 0.001), indicating a post-PBM reduction of 72% and 60% of the initial pain level, respectively. The analgesic benefit of PBM remained for a mean of 6.0 ± 5.1 days. One patient reported a transient burning sensation after one PBM session. High-power laser PBM may provide nonpharmacologic, patient-friendly, long-lasting, rapid pain relief for refractory OM.

Effectiveness of a 655-nm InGaAsP diode laser to detect subgingival calculus in patients with periodontal disease.

Previous in vitro studies have proven laser fluorescence measurement using a 655-nm Indium Gallium Arsenide Phosphide (InGaAsP) based diode laser radiation to be a useful tool to detect subgingival calculus. The aim of this prospective study was to evaluate the 655-nm InGaAsP diode laser in detecting subgingival calculus in patients with periodontal disease compared with photographic assessment during periodontal surgery. Twelve patients (six women, six men) aged between 21 and 75 years with periodontitis scheduled for periodontal surgery were included in this prospective study. All laser fluorescence measurements were made before periodontal surgery. Intraoperatively a mucoperiostal flap was performed, subgingival calculus was visualized, and photographic images were taken. The presence of calculus was recorded for each evaluated site. A total of 115 tooth surface sites of 32 teeth from the 12 patients were evaluated before (laser) and during surgery (image). Compared with image evaluation the laser assessment showed a sensitivity of 0.70 (CI0.025 0.53 to CI0.975 0.83) and a specificity of 0.97 (CI0.025 0.85 to CI0.975 0.99). The overall probability to correctly detect subgingival calculus with the laser (accuracy) was 0.82 (CI0.025 0.74 to CI0.975 0.88). The 655-nm diode laser was able to detect subgingival calculus. Hence, the 655nm diode laser may be used as an additional tool for calculus detection in non-surgical periodontal therapy.

Adjunctive use of InGaAsP and Er,Cr:YSGG lasers in nonsurgical periodontal therapy: a randomized controlled clinical study.

To evaluate clinically and microbiologically the outcomes following the combined application of InGaAsP diode laser and Er,Cr:YSGG laser for nonsurgical treatment of chronic periodontitis (ChP). Forty-two patients (age 45.31 ± 9.78 years, 22 female, 23 smokers) with ChP were randomly treated with subgingival debridement (SD) by means of ultrasonic and hand instruments (control group, n = 21) or with InGaAsP followed 1 week later by InGaAsP + SD + Er,Cr:YSGG (test group, n = 21). In the test group, a second laser treatment was performed for all residual sites (bleeding sites with probing depth [PD] ≥ 4 mm) 2 months after the first laser therapy. At baseline and 6 months after therapy, periodontal clinical and microbiologic parameters were evaluated. Six months after therapy, statistically significant clinical and microbiologic improvements (PD reduction, clinical attachment level [CAL] gain, quantitative reduction of periopathogens) were observed in both groups compared to baseline. However, the use of InGaAsP followed by SD and the adjunctive use of an Er,Cr:YSGG laser, yielded statistically significantly higher clinical (PD, CAL, bleeding on probing, number of sites with PD ≥ 5 mm, PD ≥ 6 mm, PD ≥ 7 mm) and microbiologic (Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, Prevotella intermedia, Peptostreptococcus micros, Fusobacterium nucleatum) improvements (P < .05) compared to SD alone. In patients with ChP, the adjunctive use of InGaAsP and Er,Cr:YSGG to SD may additionally improve the clinical and microbiologic parameters obtained with SD alone, thus representing a valuable approach in nonsurgical periodontal therapy.

The antibacterial effect of the combined Er,Cr:YSGG and 940 nm diode laser therapy in treatment of periodontitis: a pilot study

The aim of the study was to accurately assess the antibacterial effect of the combined Er,Cr:YSGG and InGaAsP 940 nm laser therapy on nine pathogenic bacteria in the treatment of periodontitis. Fifty-six patients were selected for this pilot study. Five patients were excluded, whereas 51 of them completed the study. The patients were randomly allocated to either the combined 2780 nm Er,Cr:YSGG (Waterlase, Biolase) and 940 nm InGaAsP diode laser (EPIC, Biolase) therapy, adjunct to scaling and root planning (SRP) (experimental group), or to scaling and root planning alone (control group). The quantitative and qualitative analysis of the total number of bacteria and nine specific germs was performed using quantitative real-time polymerase chain reaction. The total bacterial load inside the periodontal pockets was reduced both for the laser plus SRP and for the SRP alone group at the 1-month and 6-month follow-ups (p < 0.05). The laser therapy group showed a more significant bacterial reduction than the control group at the 1-month and 6-month follow-ups. The germ number reduction was statistically strongly significant for the total number of germs and for eight out of nine analyzed bacteria. The present study suggests that a combined Er,Cr:YSGG 2780 nm and diode InGaAsP 940 nm laser therapy added to the nonsurgical periodontal treatment brings an important benefit in bacterial reduction and stands as a reliable alternative to antibiotic prescriptions in periodontal treatment. The positive changes are also reflected in significant improvement of clinical periodontal parameters. The results suggest that newly formed bacterial microbiome inside the sulcus appears to be more beneficial, durable, and stable in the lased group.

Band-gap shrinkage calculations and analytic model for strained bulk InGaAsP

Band-gap shrinkage is an important effect in semiconductor lasers and optical amplifiers. In the former it leads to an increase in the lasing wavelength and in the latter an increase in the gain peak wavelength as the bias current is increased. The most common model used for carrier-density dependent band-gap shrinkage is a cube root dependency on carrier density, which is strictly only true for high carrier densities and low temperatures. This simple model, involves a material constant which is treated as a fitting parameter. Strained InGaAsP material is commonly used to fabricate polarization insensitive semiconductor optical amplifiers (SOAs). Most mathematical models for SOAs use the cube root bandgap shrinkage model. However, because SOAs are often operated over a wide range of drive currents and input optical powers leading to large variations in carrier density along the amplifier length, for improved model accuracy it is preferable to use band-gap shrinkage calculated from knowledge of the material bandstructure. In this letter the carrier density dependent band-gap shrinkage for strained InGaAsP is calculated by using detailed non-parabolic conduction and valence band models. The shrinkage dependency on temperature and both tensile and compressive strain is investigated and compared to the cube root model, for which it shows significant deviation. A simple power model, showing an almost square-root dependency, is derived for carrier densities in the range usually encountered in InGaAsP laser diodes and SOAs.

Evolution of EDFA from single-core to multi-core and related recent progress in optical communication

A compact 1.48 μm InGaAsP laser-diode (LD)-pumped erbium-doped optical fiber amplifier (EDFA) was invented in 1989 and it revolutionized optical communication in combination with a wavelength division multiplexing (WDM) technique. Recently, in addition to the existing single-core EDFA, a multi-core EDFA, which employs space division multiplexing (SDM), was developed to increase transmission capacity even further. The first half of this paper describes the evolution of the EDFA from a single-core to a multi-core device and the second half focuses on related topics in optical communication.

Temperature dependent optoelectronic properties of a non-intentionally created cleaved-coupled-cavity laser

A 1300nm InGaAsP laser diode, degraded after the application of high voltage ESD pulses in forward direction, showed after degradation a strong longitudinal mode suppression, resulting in a single mode emission spectrum identical to the one of a cleaved-coupled-cavity laser. The room temperature threshold current after ESD induced degradation increased by about 50% and the differential quantum efficiency dropped substantially. However, even after degradation in a wide temperature range stable single mode laser operation has been achieved.

Low level laser effect after micro-marsupialization technique in treating ranulas and mucoceles: a case series report

The aim of this preliminary study was to investigate the influence of low level laser therapy (LLLT) in alleviating pain caused by micro-marsupialization and the healing of oral ranulas and selected mucoceles. Eleven patients underwent micro-marsupialization treatment associated with LLLT. The patients were irradiated with a 660-nm continuous wave from an indium-gallium-arsenide-phosphorous (InGaAsP) diode laser, at 100mW, with a spot size on the tissue surface of 0.0283cm(2) (irradiance = 3.53W/cm(2)). Irradiation was carried out immediately following micro-marsupialization treatment, as well as at 24, 48, and 72h post-micro-marsupialization. All treated oral ranulas and selected mucoceles presented clinical healing. No evidence of recurrence could be identified during a mean of 11.0-month follow-up period. The use of InGaAsP diode lasers, within the parameters tested, appears to present a good alternative treatment to reduce pain and heal oral ranulas and selected mucoceles associated with micro-marsupialization.

Modeling and simulation of dispersion-limited fiber communication systems employing directly modulated laser diodes

This paper quantifies the role played by fiber dispersion in limiting the transmission distance in directly modulated gigabit optical fiber communication systems (OFCSs). The study is based on modeling and simulation of an OFCS deploying a directly modulated 1.55-μm distributed feedback InGaAsP laser diode, a single-mode fiber and a PIN photodetector. The repeater distance of the system is decided to correspond to a bit error rate of 10−9. The receiver sensitivity corresponding to the back-to-back configuration is calculated. Fiber attenuation was found to limit the maximum transmission distance to 162–202 km under bit rates ranging between 1 and 10 Gbps. This distance was found to be less affected by counting the chromatic dispersion of the fiber up to bit rate of 2 Gbps. A dramatic decrease in the transmission distance is predicted when the bit rate increases further and the system becomes dispersion limited. Influence of dispersion on the transmission distance is quantified in terms of the power penalty of the OFCS system associated with taking account of fiber dispersion. This power penalty is predicted to be within 7 dB for bit rates below 5 Gbps but jumps to values as high as 22 dB at higher bit rates.

Biostimulatory effect of low-level laser therapy on keratinocytes in vitro

Epithelial cells play an important role in reparative events. Therefore, therapies that can stimulate the proliferation and metabolism of these cells could accelerate the healing process. To evaluate the effects of low-level laser therapy (LLLT), human keratinocytes were irradiated with an InGaAsP diode laser prototype (LASERTable; 780 ± 3 nm; 40 mW) using 0.5, 1.5, 3, 5, and 7 J/cm2 energy doses. Irradiations were done every 24 h totaling three applications. Evaluation of cell metabolism (MTT assay) showed that LLLT with all energy doses promoted an increase of cell metabolism, being more effective for 0.5, 1.5, and 3 J/cm2. The highest cell counts (Trypan blue assay) were observed with 0.5, 3, and 5 J/cm2. No statistically significant difference for total protein (TP) production was observed and cell morphology analysis by scanning electron microscopy revealed that LLLT did not promote morphological alterations on the keratinocytes. Real-time polymerase chain reaction (qPCR) revealed that LLLT also promoted an increase of type I collagen (Col-I) and vascular endothelial growth factor (VEGF) gene expression, especially for 1.5 J/cm2, but no change on fibroblast growth factor-2 (FGF-2) expression was observed. LLLT at energy doses ranging from 0.5 to 3 J/cm2 promoted the most significant biostimulatory effects on cultured keratinocytes.

In Vitro Wound Healing Improvement by Low-Level Laser Therapy Application in Cultured Gingival Fibroblasts

The aim of this study was to determine adequate energy doses using specific parameters of LLLT to produce biostimulatory effects on human gingival fibroblast culture. Cells (3 × 104 cells/cm2) were seeded on 24-well acrylic plates using plain DMEM supplemented with 10% fetal bovine serum. After 48-hour incubation with 5% CO2 at 37°C, cells were irradiated with a InGaAsP diode laser prototype (LASERTable; 780 ± 3 nm; 40 mW) with energy doses of 0.5, 1.5, 3, 5, and 7 J/cm2. Cells were irradiated every 24 h totalizing 3 applications. Twenty-four hours after the last irradiation, cell metabolism was evaluated by the MTT assay and the two most effective doses (0.5 and 3 J/cm2) were selected to evaluate the cell number (trypan blue assay) and the cell migration capacity (wound healing assay; transwell migration assay). Data were analyzed by the Kruskal-Wallis and Mann-Whitney nonparametric tests with statistical significance of 5%. Irradiation of the fibroblasts with 0.5 and 3 J/cm2 resulted in significant increase in cell metabolism compared with the nonrradiated group (P < 0.05). Both energy doses promoted significant increase in the cell number as well as in cell migration (P < 0.05). These results demonstrate that, under the tested conditions, LLLT promoted biostimulation of fibroblasts in vitro.

1550 nm InGaAsP LD 광송신회로의 PSPICE 모델 및 광변조 특성 해석

The PSPICE equivalent circuit elements of a 1550 nm InGaAsP laser diode were derived by using multi-level rate equations. The device parameters were extracted by using a self-consistent numerical method for the optical gain properties of the MQW active regions. The resulting equivalent circuit model is also applied to an actual optical transmitter, and its PSPICE simulation results show good agreement with the measured results once the parasitic capacitance due to the packaging is taken into account.

In Vitro effect of low-level laser therapy on typical oral microbial biofilms

The aim of this study was to evaluate the effect of specific parameters of low-level laser therapy (LLLT) on biofilms formed by Streptococcus mutans, Candida albicans or an association of both species. Single and dual-species biofilms--SSB and DSB--were exposed to laser doses of 5, 10 or 20 J/cm(2) from a near infrared InGaAsP diode laser prototype (LASERTable; 780 ± 3 nm, 0.04 W). After irradiation, the analysis of biobilm viability (MTT assay), biofilm growth (cfu/mL) and cell morphology (SEM) showed that LLLT reduced cell viability as well as the growth of biofilms. The response of S. mutans (SSB) to irradiation was similar for all laser doses and the biofilm growth was dose dependent. However, when associated with C. albicans (DSB), S. mutans was resistant to LLLT. For C. albicans, the association with S. mutans (DSB) caused a significant decrease in biofilm growth in a dose-dependent fashion. The morphology of the microorganisms in the SSB was not altered by LLLT, while the association of microbial species (DSB) promoted a reduction in the formation of C. albicans hyphae. LLLT had an inhibitory effect on the microorganisms, and this capacity can be altered according to the interactions between different microbial species.

Performance assessment of novel side firing flexible optical fibers for dental applications

Use of lasers in dentistry in root canals of teeth and in periodontal pockets for disinfection would be more effective if energy was delivered laterally. This study examined the energy emission profiles of fibers modified in various ways to enhance their lateral emissions for dental use. Commercial optical fibers were altered by tube etching with hydrofluoric acid, modified tube etching (after removing the protective polyimide coating), alumina abrasive particle beams, and by etching and particle beams used in combination. Three free-running pulsed infrared lasers (Nd:YAG, Er:YAG, and Er,Cr:YSGG) were employed to test the modified fibers, with 25 fibers for each laser (modified or unmodified). Surface topography of fibers was examined using SEM. Laser emissions forward and laterally were measured, and thermally sensitive paper used to record the emission profiles. Visible tracing of emissions was undertaken using coaxial He-Ne or InGaAsP diode laser emissions. The etching/abrasion/etching combination gave a unique honeycomb surface configuration with grating-like properties, whilst etching alone gave a conical end. Conical and honeycomb tips showed greater lateral and lower forward emissions compared with plain fibers, with fourfold improvements in lateral emission. The most regular lateral emissions were from the honeycomb configuration. The honeycomb and the conical fiber modifications show dramatic improvements in lateral emissions. The unique emission profile obtained for the honeycomb fibers could play a significant role in increasing the efficiency of laser delivery for endodontic and periodontal applications in dentistry, as well as in other fields.

Pressure and temperature tuning of an external cavity InGaAsP laser diode

We demonstrate wide-range tuning of an 830 nm InGaAsP laser diode by pressure and temperature combined with tuning by external grating. Pressure tuning (up to 11 kbar) yields the wavelength range of 70 nm limited by the increase of the threshold current. Temperature tuning from room temperature down to 90 K yields the wavelength range of 56 nm. The reliability of the lasers subjected to pressure or temperature cycles seems to be mainly related to mounting-induced strains, i.e. the choice of proper submount is crucial. The tuning range achieved with external grating decreases at high pressure (and at low temperature).

Influence of Gain Suppression on Static and Dynamic Characteristics of Laser Diodes under Digital Modulation

This paper presents theoretical investigation of the influence of gain suppression on dynamic characteristics of InGaAsP laser diodes under digital modulation. The study is based on numerical solution of the laser rate equations in which the bias current is augmented by a digital signal with norreturn to zero coding. The modulation characteristics include the eye diagram, turn-on jitter and quality factor of the modulated laser signal. Nonlinear gain is found to improve the eye-diagram quality by increasing the quality factor and reducing the turn-on jitter. Influence of gain suppression on frequency chirp induced by the temporal carrier-induced variation of the refraction change at high bit rates is also illustrated.

In situ resistance measurement of the p-type contact in InP–InGaAsP coolerless ridge waveguide lasers

Scanning voltage microscopy (SVM) is employed to measure the voltage division—and resulting contact resistance and power loss—at the p-In0.53Ga0.47As–p-InP heterojunction in a working InP–InGaAsP laser diode. This heterojunction is observed to dissipate ∼35% of the total power applied to the laser over the operating bias range. This in situ experimental study of the parasitic voltage division (and resulting power loss and series contact resistance) highlights the need for a good p-type contact strategy. SVM technique provides a direct, fast and in situ measurement of specific contact resistance, an important device parameter.

Characterisation and optimisation of a dual-channel picosecond gain-switched DFB laser system for use as a pump–probe source

The output characteristics of a dual-channel gain-switched laser system are studied with respect to the gain-switch frequency and power. InGaAsP laser diodes operating at 1548 and 1549 nm are gain-switched at 1 GHz and the spectral and temporal profiles of the pulses are investigated. The development of a pump–probe system with the use of in-line amplifiers and amplified spontaneous emission filtering is detailed.

Diode Laser (980 nm) as Adjunct to Scaling and Root Planing

The aim of this study was to evaluate clinical efficacy of InGaAsP diode laser as adjunct to traditional scaling and root planing. The use of laser is one of the most recent methods in nonsurgical periodontal treatment. Efficacy and side effects of each type of laser treatment have yet to be determined. Thirty patients suffering from moderate periodontal disease have been considered. They were randomly selected to undergo either scaling and root planing with curets, or scaling and root planing combined with InGaAsP laser (980 nm and 2 W). The papilla bleeding index (PBI), bleeding on probing (BOP), and clinical attachment level (CAL) were registered at the beginning and end of treatment. At the end of treatment, PBI average in the group treated with laser was 0.24 versus 0.43 in the group under conventional treatment (p = 0.014). In the group undergoing scaling and root planing, BOP decrease is 19.55% less (p < 0.0001) than in the group also treated with laser. Nevertheless, CAL differences cannot be considered significant between both groups (p = 0.67). Scaling and root planing in combination with laser produce moderate clinical improvement over traditional treatment.