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  1. Fulltext Tuning range characteristics of linear cavity L-band multiwavelength brillouin-erbium fibre laser
    Al-Mansoori, M.H., Mahdi, M.A., Iqbal, S.J., Abdullah, M.K.
    ASM Science Journal, 2008;2(2):107-113.
    MyJurnal
    In this paper, the tuning range characteristics of a multiwavelength L-band Brillouin-erbium fibre laser utilizing a linear cavity is described. The dependency of the Stokes signal tuning range on the laser’s pumping power and single mode fibre length is elaborated. The proposed laser configuration exhibited a wide tuning range of 11 nm from 1599 nm to 1610 nm. The maximum number of 28 output channels with a spacing of 10.5 GHz was achieved by setting the Brillouin pump wavelength and power at 1603.1 nm and 1.1 mW, respectively. The wider tuning range and higher number of Brillouin Stokes contributed to the higher efficiency of doublepass amplification in the erbium gain medium and also to the bidirectional generation of Brillouin Stokes in the single-mode fibre.
    Matched MeSH terms: Lasers, Solid-State
  2. Fulltext An erbium/ytterbium co-doped fibre amplifier using 1058 nm pumping
    Harun, S.W., Tamjis, M.R., Muhd-Yassin, S.Z., Abd-Rahman, M.K., Ahmad, H.
    ASM Science Journal, 2007;1(2):129-133.
    MyJurnal
    This paper demonstrates an erbium/ytterbium co-doped fi bre amplifi er (EYDFA) which used a pumping wavelength of 1058 nm, whereby the amplifi cation was assisted by the energy transfer between Yb and Er ions. The energy transfer increased the erbium doping concentration limit that was imposed by concentration quenching in erbium-doped fi bre. The optimum length was obtained at 4m~6m for erbium/ytterbium co-doped fi bre with Er ion concentration of 1000 p.p.m. This enabled the development of a compact amplifi er with a shorter gain medium compared to erbium-doped fi bre amplifi ers which use a gain medium of up to 15 m. A 1058 nm pumping wave-length was used for the EYDFA, as 1480 nm pumping resulted in severely degraded gain and noise fi gures because the energy transfer could not be achieved. The use of the optical isolator improved the small signal gain and noise fi gure by about 4.8 dB and 1.6 dB, respectively. Without the isolator, gain saturation and a noise fi gure penalty were observed due to the oscillating laser which was created at around 1534 nm by spurious refl ection. This showed that the usage of optical isolators was an important aspect to consider when designing an EYDFA.
    Matched MeSH terms: Lasers
  3. Fulltext Distributed feedback Er-Yb co-doped phosphate fibre laser
    Harun, S.W., Hofmann, P., Schulzgen, A., Li, L., Peyghambarian, N., Ahmad, H.
    ASM Science Journal, 2008;2(2):149-152.
    MyJurnal
    A distributed feedback fibre laser made of highly Er-Yb co-doped phosphate glass fibre was demonstrated experimentally. The 45 mm long fibre laser device operated at 1540 nm with more than 50 dB side mode suppression ratio. However, the output power was still relatively lower due to un-optimized grating structure and thermal management.
    Matched MeSH terms: Lasers
  4. Fulltext Effect of Laser and Energy-based Device Therapies to Minimize Surgical Scar Formation: A Systematic Review and Network Meta-analysis
    Yenyuwadee S, Achavanuntakul P, Phisalprapa P, Levin M, Saokaew S, Kanchanasurakit S, et al.
    Acta Derm Venereol, 2024 Jan 08;104:adv18477.
    PMID: 38189223 DOI: 10.2340/actadv.v104.18477
    Utilization of lasers and energy-based devices for surgical scar minimization has been substantially evaluated in placebo-controlled trials. The aim of this study was to compare reported measures of efficacy of lasers and energy-based devices in clinical trials in preventing surgical scar formation in a systematic review and network meta-analyses. Five electronic databases, PubMed, Scopus, Embase, ClinicalTrials.gov, and the Cochrane Library, were searched to retrieve relevant articles. The search was limited to randomized controlled trials that reported on clinical outcomes of surgical scars with treatment initiation no later than 6 months after surgery and a follow-up period of at least 3 months. A total of 18 randomized controlled trials involving 482 participants and 671 postsurgical wounds were included in the network meta-analyses. The results showed that the most efficacious treatments were achieved using low-level laser therapy) (weighted mean difference -3.78; 95% confidence interval (95% CI) -6.32, -1.24) and pulsed dye laser (weighted mean difference -2.46; 95% CI -4.53, -0.38). Nevertheless, low-level laser therapy and pulsed dye laser demonstrated comparable outcomes in surgical scar minimization (weighted mean difference -1.32, 95% CI -3.53, 0.89). The findings of this network meta-analyses suggest that low-level laser therapy and pulsed dye laser are both effective treatments for minimization of scar formation following primary closure of surgical wounds with comparable treatment outcomes.
    Matched MeSH terms: Lasers, Dye*
  5. Comparison of accuracy and reliability of CBCT and 3D laser scanner in the volumetric assessment of the root canal space
    Thomas AR, Soe HHK, Silva CS, Kaur H, Ganendrah LD, Gomez LM
    Am J Dent, 2023 Oct;36(5):246-250.
    PMID: 37865812
    PURPOSE: To compare the accuracy and reliability of cone-beam computed tomography (CBCT) and laser scanner in measuring minor volume changes such as the root canal space.

    METHODS: 35 maxillary incisors were endodontically prepared. A dimensionally stable silicone material was injected into the root canal space and scanned with CBCT. The root canal volume was measured using Romexis 3.0.1 R software. Replicas were carefully removed from the teeth and scanned using an extraoral laser scanner. These images were exported to the Rhinoceros software for volume measurement. The volume of each replica was also assessed using the gravimetric method. To determine the accuracy, the volume obtained from both devices was compared with the gravimetric method. Statistical analysis was done using a paired t-test. The reliability was assessed using the intraclass correlation coefficient.

    RESULTS: There was no statistically significant difference between the mean volume of CBCT 27.04 ± 7.25 mm³ and the mean volume of the gravimetric method 27.87 ± 7.17 mm³ (P< 0.05). A statistically significant difference was seen with the laser scanner at 25.31 ± 6.89 mm³ and the gravimetric method at 27.87 ± 7.17 mm³ (P< 0.05). CBCT showed a good degree of agreement (ICC 0.899), while the laser scanner showed a moderate degree of agreement (ICC 0.644) with the gravimetric method. CBCT proved accurate and reliable in measuring minor volumes like the root canal space, ideally in the range of 20-25 mm³. The laser scanner presented acceptable reliability.

    CLINICAL SIGNIFICANCE: The laboratory data showed satisfactory outcomes, providing an evidence-based approach and potentially motivating clinicians to integrate cone-beam computed tomography for volume analysis into clinical practice. The accuracy and reliability of laser scanners for small-volume analysis have not previously been evaluated. Consequently, the findings from this study warrant further clinical investigations.

    Matched MeSH terms: Lasers
  6. Effect of a single dose of low-level laser therapy on spontaneous and chewing pain caused by elastomeric separators
    Qamruddin I, Alam MK, Fida M, Khan AG
    Am J Orthod Dentofacial Orthop, 2016 Jan;149(1):62-6.
    PMID: 26718379 DOI: 10.1016/j.ajodo.2015.06.024
    The aim of this study was to see the effect of a single dose of low-level laser therapy on spontaneous and chewing pain after the placement of elastomeric separators.
    Matched MeSH terms: Lasers, Semiconductor/therapeutic use
  7. Fulltext Light-Addressable Potentiometric Sensors Using ZnO Nanorods as the Sensor Substrate for Bioanalytical Applications
    Tu Y, Ahmad N, Briscoe J, Zhang DW, Krause S
    Anal Chem, 2018 07 17;90(14):8708-8715.
    PMID: 29932632 DOI: 10.1021/acs.analchem.8b02244
    Light-addressable potentiometric sensors (LAPS) are of great interest in bioimaging applications such as the monitoring of concentrations in microfluidic channels or the investigation of metabolic and signaling events in living cells. By measuring the photocurrents at electrolyte-insulator-semiconductor (EIS) and electrolyte-semiconductor structures, LAPS can produce spatiotemporal images of chemical or biological analytes, electrical potentials and impedance. However, its commercial applications are often restricted by their limited AC photocurrents and resolution of LAPS images. Herein, for the first time, the use of 1D semiconducting oxides in the form of ZnO nanorods for LAPS imaging is explored to solve this issue. A significantly increased AC photocurrent with enhanced image resolution has been achieved based on ZnO nanorods, with a photocurrent of 45.7 ± 0.1 nA at a light intensity of 0.05 mW, a lateral resolution as low as 3.0 μm as demonstrated by images of a PMMA dot on ZnO nanorods and a pH sensitivity of 53 mV/pH. The suitability of the device for bioanalysis and bioimaging was demonstrated by monitoring the degradation of a thin poly(ester amide) film with the enzyme α-chymotrypsin using LAPS. This simple and robust route to fabricate LAPS substrates with excellent performance would provide tremendous opportunities for bioimaging.
    Matched MeSH terms: Lasers
  8. Fulltext The Effects Of CO2 Laser On Oral Lichen Planus And Lichenoid Lesions
    Kok, T.C., Ong, S.T.
    Ann Dent, 2001;8(1):-.
    MyJurnal
    The purpose of this study is to assess the effectiveness of C02 laser in relieving symptoms associated with Oral lichen planus (aLP) and lichenoid lesions (aLL) and the event of healing. Six patients were selected for this study with 13 sites treated. Each lesion was ablated with C02 laser and the wound allowed to heal undisturbed. Prior to treatment, 4 patients had both unprovoked and provoked pain and 2 patients rated for provoked pain only. After laser ablation, five out of six patients treated recorded no pain / 0 pain score. One month post-laser, the treated area was almost the same colour as the surrounding normal mucosa and soft in texture in all but one patient in which there was some fibrosis and residual plaque-like patch. Weconclude that the use of C02 laser in the treatment of aLP and aLL shows positive results in relieving symptoms associated with these lesions.
    Matched MeSH terms: Lasers
  9. Fulltext The Thermal Effect Associated With CO2 Laser Gingivecttomy Of Tissues Surrounding Plasma Coated Titanium Implants. A Preliminary Study
    Mahmood, W.A., Watkinson, A.C., Rooney, J.
    Ann Dent, 2000;7(1):-.
    MyJurnal
    The CO2 laser has been actively used clinically for soft tissue surgery. The advantages have been widely acknowledged. In implant related tissue surgery, the use .6f CO2 laser has been debated on whether the heat generated during the procedure would be detrimental to the bone thus losing the implants through disosseointegration. In this preliminary work, CO2 laser was used to perform a simulated gingivectomy of tissue surrounding plasma coated titanium implants. The purpose was to observe the pattern of heat generated at different levels of the implant body. The safe power range and standard precaution was also identified. The results suggested that power output between 6 Watt to 8 Watt in repeated pulsed mode with duration of 5 seconds is considered safe. With this mode the operator
    Matched MeSH terms: Lasers, Gas
  10. Characteristics of multiwavelength L-band Brillouin-Raman fiber laser under forward and backward pumped environment
    Abass AK, Al-Mansoori MH, Jamaludin MZ, Abdullah F, Al-Mashhadani TF
    Appl Opt, 2013 Jun 1;52(16):3764-9.
    PMID: 23736332 DOI: 10.1364/AO.52.003764
    We experimentally investigate the performance of L-band multiwavelength Brillouin-Raman fiber laser (MBRFL) under forward and backward pumped environments utilizing a linear cavity. A short length of 1.18 km dispersion compensating fiber is used as a nonlinear gain medium for both Brillouin and Raman gain. Experimental results indicate that the gain in the copumped laser configuration is higher than the gain in the counterpumped configuration. A stable and constant number of Brillouin Stokes lines up to 23 Stokes, with channel spacing of 0.08 nm and more than 20 dB of optical signal to noise ratio, can be generated as well as tuning over 20 nm in the L-band region from 1570 to 1590 nm. The laser generating the Brillouin Stokes lines exhibits flat amplitude bandwidth and high average output power of 0.8 and 1.6 dBm for the copropagation and counterpropagation pumps, respectively. Moreover, the tuning range bandwidth of the MBRFL can be predicted from the oscillated Brillouin pump gain profile.
    Matched MeSH terms: Lasers
  11. S-band multiwavelength Brillouin/Raman distributed Bragg reflector fiber lasers
    Zulkifli MZ, Ahmad H, Taib JM, Muhammad FD, Dimyati K, Harun SW
    Appl Opt, 2013 Jun 1;52(16):3753-6.
    PMID: 23736330 DOI: 10.1364/AO.52.003753
    A multiwavelength Brillouin/Raman distributed Bragg reflector fiber laser operating in the S-band region is proposed and demonstrated. The laser uses a 7.7 km long dispersion-shifted fiber with an effective mode area of 15 μm(2) as the Brillouin and Raman gain media simultaneously. Two 1420 nm laser diodes with a combined power of 372 mW are used as pump sources, while a fiber Bragg grating with a center wavelength of 1500 nm is used as a reflector in the cavity. The setup is capable of generating 6 clearly defined Stokes lines at the highest pump power, spanning from 1499.8 to 1500.3 nm with the even Stokes having relatively higher peak powers, between 1.4 and 3.5 dBm as compared to the odd Stokes, which have peak powers between -4.7 and -5.0 dBm. The output of the laser is very stable and shows little to no fluctuations over a monitoring period of 50 min.
    Matched MeSH terms: Lasers, Semiconductor
  12. S-band multiwavelength ring Brillouin/Raman fiber laser with 20 GHz channel spacing
    Ahmad H, Zulkifli MZ, Hassan NA, Harun SW
    Appl Opt, 2012 Apr 10;51(11):1811-5.
    PMID: 22505174 DOI: 10.1364/AO.51.001811
    We propose and demonstrate a tunable S-band multiwavelength Brillouin/Raman fiber laser (MBRFL) with a tuning range of between 1490 to 1530 nm. The proposed MBRFL is designed around a 7.7 km long dispersion compensating fiber in a simple ring configuration, acting as a nonlinear medium for the generation of multiple wavelengths from stimulated Brillouin scattering (SBS) and also as a nonlinear gain medium for stimulated Raman scattering (SRS) amplification. A laser source with a maximum power of 12 dBm acts as the Brillouin pump (BP), while two 1420 nm laser diodes with a total power of 26 dBm act as the Raman pumps (RPs). The MBRFL can generate a multiwavelength comb consisting of even and odd Stokes at an average power of -12 dBm and -14 dBm respectively, and by separating the even and odd Stokes outputs, a 20 GHz channel spacing is obtained between two consecutive wavelengths. Due to the four-wave mixing (FWM) effect, anti-Stokes lines are also observed. The multiwavelength comb generated is not dependent on the BP, thus providing high stability and repeatability and making it a highly potential source for many real-world applications. This is the first time, to the knowledge of the authors, that a tunable MBRFL has been developed using SRS to obtain gain in the S-band region.
    Matched MeSH terms: Lasers, Semiconductor
  13. Contribution of Rayleigh scattering on Brillouin comb line generation in Raman fiber laser
    Zamzuri AK, Al-Mansoori MH, Samsuri NM, Mahdi MA
    Appl Opt, 2010 Jun 20;49(18):3506-10.
    PMID: 20563203 DOI: 10.1364/AO.49.003506
    We demonstrate the generation of multiple Brillouin Stokes lines generation assisted by Rayleigh scattering in Raman fiber laser. The linear cavity is utilized to take advantage of the Rayleigh scattering effect, and it also produces two strong spectral peaks at 1555 and 1565nm. Under a strong pumping condition, the Rayleigh backscatters contribute to the oscillation efficiency, which increases the Brillouin Stokes lines intensity between these two wavelength ranges. The multiple Stokes lines get stronger by suppressing the buildup of free-running longitudinal modes in the laser structure.
    Matched MeSH terms: Lasers
  14. Reduction of gain depletion and saturation on a Brillouin-erbium fiber laser utilizing a Brillouin pump preamplification technique
    Al-Mansoori MH, Mahdi MA
    Appl Opt, 2009 Jun 20;48(18):3424-8.
    PMID: 19543350
    This paper presents the characteristics of a multiwavelength L-band Brillouin-erbium comb fiber laser with a preamplified Brillouin pump (BP) power technique at low pumping powers. The issue of erbium-doped fiber gain depletion and Brillouin gain saturation are resolved by the proposed structure. For long single-mode fiber length, the Stokes line emission occurs at low pumping powers because of the high strength of spontaneous Brillouin scattering, which provides a strong seed for coherent regenerative amplification of the Stokes line in the laser cavity. The laser structure achieves a low threshold power of 17 mW and is able to produce high number of output channels at low pumping powers. We experimentally show that the fiber laser structure can produce up to 37 channels at 55 and 0.045 mW of 1480 nm pump and BP powers, respectively.
    Matched MeSH terms: Lasers, Solid-State
  15. Opto-optical gain-clamped L-band erbium-doped fiber amplifier with C-band control signal
    Bakar AA, Mahdi MA, Al-Mansoori MH, Shaari S, Zamzuri AK
    Appl Opt, 2009 Apr 20;48(12):2340-3.
    PMID: 19381186
    We demonstrate an opto-optical gain-clamped L-band erbium-doped fiber amplifier by manipulating the C-band lasing wavelength as the control signal. The L-band gain-clamped value is achieved by tuning the control laser in the C-band wavelength range that propagates in the opposite direction to the L-band signal. Within the wavelength range of 1538 nm and 1560 nm, the L-band gain decreases linearly with the increment of the C-band lasing wavelength. The L-band gain dynamic range decreases with the increment of the cavity loss. By combining two different levels of cavity loss, the gain dynamic range of 10 dB from 11 dB to 21 dB is achieved with an average noise figure of less than 5.9 dB. The whole gain spectrum of the L-band can be used for multiple-channel amplification because the laser is created outside its signal band.
    Matched MeSH terms: Lasers
  16. Optimization of output coupling ratio on the performance of a ring-cavity Brillouin-erbium fiber laser
    Hambali NA, Mahdi MA, Al-Mansoori MH, Saripan MI, Abas AF
    Appl Opt, 2009 Sep 20;48(27):5055-60.
    PMID: 19767918 DOI: 10.1364/AO.48.005055
    The operation of a single-wavelength Brillouin-erbium fiber laser (BEFL) system with a Brillouin pump preamplified technique for different output coupling ratios in a ring cavity is experimentally demonstrated. The characteristics of Brillouin Stokes power and tunability were investigated in this research. The efficiency of the BEFL operation was obtained at an optimum output coupling ratio of 95%. By fixing the Brillouin pump wavelength at 1550 nm while its power was set at 1.6 mW and the 1480 pump power was set to its maximum value of 135 mW, the Brillioun Stokes power was found to be 28.7 mW. The Stokes signal can be tuned within a range of 60 nm from 1520 to 1580 nm without appearances of the self-lasing cavity modes in the laser system.
    Matched MeSH terms: Lasers, Solid-State
  17. Nanosecond soliton pulse generation by mode-locked erbium-doped fiber laser using single-walled carbon-nanotube-based saturable absorber
    Ismail MA, Harun SW, Zulkepely NR, Nor RM, Ahmad F, Ahmad H
    Appl Opt, 2012 Dec 20;51(36):8621-4.
    PMID: 23262603 DOI: 10.1364/AO.51.008621
    We demonstrate a simple and low cost mode-locked erbium-doped fiber laser (EDFL) operating in the nanosecond region using a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA). A droplet of SWCNT solution is applied on the end of a fiber ferrule, which is then mated to another clean connector ferrule to construct an SA. Then the SA is integrated into a ring EDFL cavity for nanosecond pulse generation. The EDFL operates at around 1570.4 nm, with a soliton-like spectrum with small Kelly sidebands, which confirms the attainment of the anomalous dispersion. It produces a soliton pulse train with a 332 ns width, repetition rate of 909.1 kHz, an average output power of 0.31 mW, and energy of 0.34 nJ at the maximum pump power of 130.8 mW.
    Matched MeSH terms: Lasers, Solid-State
  18. Mode-locked thulium-bismuth codoped fiber laser using graphene saturable absorber in ring cavity
    Zen DI, Saidin N, Damanhuri SS, Harun SW, Ahmad H, Ismail MA, et al.
    Appl Opt, 2013 Feb 20;52(6):1226-9.
    PMID: 23434993 DOI: 10.1364/AO.52.001226
    We demonstrate mode locking of a thulium-bismuth codoped fiber laser (TBFL) operating at 1901.6 nm, using a graphene-based saturable absorber (SA). In this work, a single layer graphene is mechanically exfoliated using the scotch tape method and directly transferred onto the surface of a fiber pigtail to fabricate the SA. The obtained Raman spectrum characteristic indicates that the graphene on the core surface has a single layer. At 1552 nm pump power of 869 mW, the mode-locked TBFL self starts to generate an optical pulse train with a repetition rate of 16.7 MHz and pulse width of 0.37 ps. This is a simple, low-cost, stable, and convenient laser oscillator for applications where eye-safe and low-photon-energy light sources are required, such as sensing and biomedical diagnostics.
    Matched MeSH terms: Lasers
  19. Highly stable graphene-assisted tunable dual-wavelength erbium-doped fiber laser
    Ahmad H, Latif AA, Abdul Khudus MI, Zulkifli AZ, Zulkifli MZ, Thambiratnam K, et al.
    Appl Opt, 2013 Feb 1;52(4):818-23.
    PMID: 23385923 DOI: 10.1364/AO.52.000818
    A highly stable tunable dual-wavelength fiber laser (TDWFL) using graphene as a means to generate a highly stable output is proposed and generated. The TDWFL comprises a 1 m long, highly doped erbium-doped fiber (EDF) acting as the linear gain medium, with a 24-channel arrayed waveguide grating acting as a wavelength slicer as well as a tuning mechanism to generate different wavelength pairs. The tuned wavelength pairs can range from 0.8 to 18.2 nm. A few layers of graphene are incorporated into the laser cavity to induce the four-wave-mixing effect, which stabilizes the dual-wavelength output by suppressing the mode competition that arises as a result of homogenous broadening in the EDF.
    Matched MeSH terms: Lasers
  20. Characterization of a multiwavelength Brillouin-erbium fiber laser based on a linear cavity configuration
    Al-Mansoori MH, Saharudin S, Abdul-Rashid H, Mahdi MA, Abdullah MK
    Appl Opt, 2005 May 10;44(14):2827-31.
    PMID: 15943335
    We experimentally demonstrate a simple method for generating a multiwavelength Brillouin comb by utilizing a linear cavity of hybrid Brillouin-erbium fiber lasers (BEFLs). The optimization of Brillouin pump wavelength, power, and erbium gain played a significant role in determining the maximum number of Brillouin Stokes signals generated. Simultaneous and stable multiple-wavelength laser output of 22 lines with 10.88-GHz channel spacing has been obtained with good flatness. Various parameters such as 980-nm pump power, Brillouin pump wavelength, and Brillouin pump power that affect the performance of a multiwavelength BEFL system have been investigated. An analysis of the tuning range of the system is presented.
    Matched MeSH terms: Lasers, Solid-State
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