High-power Ho Research Articles

Thulium or holmium laser or both: where will the journey take us?

The Holmium:YAG laser has been the gold standard for laser lithotripsy over the past three decades and, since the late 1990s, also for prostate enucleation. Pulsed thulium fibre lasers (TFL) demonstrated their efficacy in in-vitro experiments and were introduced to the market a few years ago. Initial clinical results for TFL in lithotripsy and enucleation are very promising. In addition to TFL, a pulsed Thulium:YAG solid-state laser has been introduced, but clinical data for this laser are currently limited. This article aims to review the key technological differences between Ho:YAG lasers and pulsed thulium lasers and compare/discuss the initial clinical results for stone lithotripsy and laser enucleation.In-vitro studies have demonstrated the technical superiority of TFL compared with Ho:YAG lasers. However, as TFL is still a new technology, only limited studies are available to date, and optimal settings for lithotripsy have not been established. For enucleation, the differences of TFL compared with a high-power Ho:YAG laser seem to be clinically irrelevant. Initial studies on pulsed Tm:YAG lasers show good results, but there continues to be a lack of comparative studies.Based on the current literature, pulsed thulium lasers have the potential of being an alternative to Ho:YAG lasers. However, further studies are necessary to determine the optimal laser technology for enucleation and lithotripsy of urinary stones, considering all parameters, including efficacy, safety, and cost.

Observation and comparison of gas formation during holmium:YAG laser lithotripsy of cystine, uric acid, and calcium oxalate stones: a chromatographic and electron microscopic analysis.

The primary aim of the present in vitro study is to analyze the chemical content of the bubbles occurring during the fragmentation of cystine stones with both the high-power and low-power holmium:YAG (Ho:YAG) lasers. The secondary aim is to discuss their clinical importance. Three types of human renal calculi calcium oxalate monohydrate (COM), cystine, and uric acid were fragmented with both low-power and high-power Ho:YAG lasers in separate experimental setups at room temperature, during which time it was observed whether gas was produced. After laser lithotripsy, a cloudy white gas was obtained, after the fragmentation of cystine stones only. A qualitative gas content analysis was performed with a gas chromatography-mass spectrometry (GC-MS) device. The fragments in the aqueous cystine calculi setup were dried and taken to the laboratory to be examined by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction analysis. No gas production was observed after fragmentation in the COM and uric acid stones. Free cystine, sulfur, thiophene, and hydrogen sulfide gas were produced by both low-power and high-power Ho:YAG laser lithotripsy of the cystine stones. In the SEM-EDX mapping analysis, a free cystine molecule containing 42.8% sulfur (S), 21% oxygen (O), 14.9% carbon (C), and 21% nitrogen (N) atoms was detected in the cystine stone experimental setup. The evidence obtained, which shows that hydrogen sulfide emerges in the gaseous environment during Ho:YAG laser fragmentation of cystine stones, indicates that caution is required to prevent the risk of in vivo production and toxicity.

Ureteroscopy and lasertripsy with pop dusting using high power holmium laser for large urinary stones > 15mm: 6.5-year prospective outcomes from a high-volume stone center.

Ureteroscopy and stone lasertripsy (URSL) is a recognized technique for treatment of urinary tract stones. Holmium:Yag laser has been successfully used for this purpose for the last two decades. More lately, pulse modulation with Moses technology and high power lasers have been introduced with the result of faster and more efficient stone lasertripsy. Pop dusting is a two-stage combined treatment using a long pulse Ho:YAG laser, initially in contact mode with the stone 'dusting' (0.2-0.5J/40-50Hz) followed by non-contact mode 'pop-dusting' (0.5-0.7J/20-50Hz). We wanted to look at the outcomes of lasertripsy for renal and ureteric stones using a high-power laser machine. Over a period of 6.5years (January 2016-May 2022), we prospectively collected data for patients undergoing URSL for stones larger than 15mm treated using high power Ho:YAG laser (60W Moses or 100W laser). Patient parameters, stone demographics and outcomes of URSL were analyzed. A total of 201 patients, underwent URSL for large urinary stones. In 136 patients (61.6%) stones were multiple and the mean single and cumulative stone size was 18mm and 22.4mm respectively. A pre- and post-operative stent was placed in 92 (41.4%) and 169 (76%) respectively. The initial and final stone free rate (SFR) were 84.5% and 94% respectively and 10% patients underwent additional procedure to achieve stone free status. 7 (3.9%) complications were recorded, all related to UTI/sepsis, with 6 Clavien II and 1 Clavien IVa complication. Dusting and pop-dusting has shown to be successful and safe with the ability to treat large, bilateral or multiple stones with low retreatment and complication rates.

High power Ho:Y2O3 ceramic laser with controllable output intensity profile at 2.1 µm.

We report on a high-power Ho:Y2O3 ceramic laser at 2.1 µm with controllable output beam profile ranging from LG01 donut, flat-top to TEM00 mode using a simple two-mirror resonator. In-band pumped at 1943nm using a Tm fiber laser beam shaped via a coupling optics comprising a capillary fiber and lens-combination to achieve distributed pump absorption in Ho:Y2O3 and hence selective excitation of the target mode, the laser yields 29.7 W of LG01 donut, 28.0 W of crater-like, 27.7 W of flat-top and 33.5 W of TEM00 mode output for absorbed pump power of 53.5 W, 56.2 W, 57.3 W and 58.2 W, respectively, corresponding to a slope efficiency of 58.5%, 54.3%, 53.8% and 61.2%. This is, to the best of our knowledge, the first demonstration of laser generation with continuously tunable output intensity profile at ∼2 µm wavelength region.

Thermal-birefringence-induced depolarization in a 450 W Ho:YAG MOPA system.

We demonstrated an efficient, high-power Ho:YAG master-oscillator power amplifier (MOPA) system and investigated its thermal-birefringence-induced depolarization. The maximum output power was 450 W with a depolarized power of 32.1 W and depolarization of 0.071 via three power amplifiers. To our knowledge, this is the highest average power generated from a Ho:YAG MOPA system. In theory, a simplified model was built to calculate the depolarization in the amplifier, and the theoretical results agreed with the actual value well. Moreover, the overall optical-to-optical efficiency of the MOPA system was near 60%, and the beam quality M2 factors of s-polarized laser were measured to be ∼ 1.8 at 400 W. In pulse operation, the per pulse energy was ∼ 11 mJ at the pulse repetition frequency of 40 kHz with the corresponding peak power of 220 kW.

What is the impact of pulse modulation technology, laser settings and intraoperative irrigation conditions on the irrigation fluid temperature during flexible ureteroscopy? An in vivo experiment using artificial stones.

To investigate the effect of different combinations of laser power settings and irrigation conditions using the pulse modulation technology of Quanta™ on irrigation fluid temperature (IFT) during FURS (flexible ureteroscopy) on an in-vivo porcine model with artificial stones. A female pig was used. Following the insertion of artificial stones (Begostone™, BEGO USA, Lincoln, RI), a K-type thermocouple was fixed to the created percutaneous access tract. Real-time recordings of IFT during FURS were performed without UAS (ureteral access sheath), with 10/12 UAS, 12/14 UAS and 14/16 UAS. Stone fragmentation was achieved using Quanta Litho Cyber Ho 150W™ (Samarate, Italy). The IFT was recorded for 30s, during laser activation, with power settings of 20, 40, 60, 75 and 100W under both manual pump and gravity irrigation. The IFT rise above 54°C was recorded above a power of 40W when gravity irrigation was used. The use of UAS prolonged the time for IFT to reach high values, although high power settings increase IFT within seconds from the laser activation. Under pump irrigation, only the 100W power setting without the use of UAS resulted in dangerous IFT after approximately 10s. The high-power Ho:YAG laser can cause a damaging thermal effect to the kidney exceeding the threshold of 54°C, under gravity irrigation. Lower power settings (up to 40W) can be used with safety. According to our experiment, when using high power settings, the use of UAS and manual pump irrigation, is the safest combination regarding renal thermal damage.

Can cystinuria decrease the effectiveness of RIRS with high-power ho:yag laser in children? Outcomes from a tertiary endourology referral center.

Cystinuria, which is the cause of cystine urolithiasis, accounts for 2-6% of all urinary stones in children, has a low prevalence with a high recurrence rate, making this metabolic disorder a therapeutic challenge in pediatric population. The aim of this work is evaluate the efficacy and safety of retrograde intra-renal surgery (RIRS) in pediatric patients with cystinuria and kidney stones smaller than 2cm. Prospective study of 64 stones treated in 22 retrograde intra-renal surgeries (RIRS) in cystinuric pediatric patients with renal or proximal ureteral stones less than 2cm. Average age of 9.5years. The following data were analyzed: demographics, stone characteristics and surgical data with intra- and postoperative complications. Location of the stones was 68.7% in the calyces, 20.3% in the renal pelvis, and 9.3% in the ureteropelvic junction; 41% of cases had multiple locations. The average cystinuria level before the procedure was 825mg/dL. The anatomy of 73% of the interventions increased the difficulty of flexible ureteroscopy and decreased stone free rates, because distorted renal anatomy was present: sclerosis of the pelvis or infundibulum, abnormal calyceal dilations, or excluded calyces. Intraoperative complications occurred in 18.2% of the procedures. Reno-vesical ultrasound was performed in all patients in the first postoperative month, with an SFR of 59%. Cystinuric patients are a challenge for pediatric urologists, decreasing the effectiveness of RIRS. However, it could be better treatment than SWL and with fewer complications than PCNL in the pediatric population with this disease.

Research Progress of High-Power Ho∶YAG Lasers and Its Application for Pumping Mid-Far-Infrared Nonlinear Frequency Conversion in ZGP, BGSe and CdSe Crystals

Research Progress of High-Power Ho∶YAG Lasers and Its Application for Pumping Mid-Far-Infrared Nonlinear Frequency Conversion in ZGP, BGSe and CdSe Crystals

Experimental ex-vivo performance study comparing a novel, pulsed thulium solid-state laser, chopped thulium fibre laser, low and high-power holmium:YAG laser for endoscopic enucleation of the prostate

PurposeThe aim of this study was to compare the enucleation performances of four different types of laser devices in an ex-vivo experiment: a novel, pulsed Tm:YAG solid-state laser evaluation model (p-Tm:YAG), chopped thulium fibre laser (TFL), low-power Ho:YAG laser (LP-Ho:YAG), and a high-power Ho:YAG laser (HP-Ho:YAG).MethodsOur primary aim was to endoscopically separate the fascial layers of a porcine belly using laser fibres within a time period of 60 s. The size of a “tissue pocket” was assessed numerically. The enucleation characteristics reflecting the surgeon’s experience were evaluated via the NASA Task Load Index (TLX) questionnaire and a questionnaire based on Likert scale.ResultsHP-Ho:YAG achieved with the available laser settings the largest overall “tissue pocket” (31.5 cm2) followed by p-Tm:YAG (15 cm2), TFL (12 cm2), and LP-Ho:YAG (6 cm2). The coagulation performances of p-Tm:YAG and TFL were rated the best. In the performance evaluation by the Likert questionnaire, HP-Ho:YAG (average score of 4.06) was rated highest, followed by p-Tm:YAG (3.94), TFL (3.38), and LP-Ho:YAG (3.25). The evaluation of the NASA-TLX performance questionnaire revealed average scores for HP-Ho:YAG, LP-Ho:YAG, TFL and p-Tm:YAG of 4.38, 4.09, 3.92 and 3.90, respectively.ConclusionWe are the first to compare different laser devices and settings in an ex-vivo study. We found that the surgeons were most satisfied with the HP-Ho:YAG laser device, followed by the p-Tm:YAG. These findings could be highly relevant for future research and for the practical utilisation of laser systems in endourology.

PD26-07 IMAGE DISTORTION DURING FLEXIBLE URETEROSCOPY: A LABORATORY MODEL COMPARING SUPER PULSE THULIUM FIBER (SPTF) LASER VS HIGH POWER HO:YAG LASER

You have accessJournal of UrologyStone Disease: Surgical Therapy III (PD26)1 Sep 2021PD26-07 IMAGE DISTORTION DURING FLEXIBLE URETEROSCOPY: A LABORATORY MODEL COMPARING SUPER PULSE THULIUM FIBER (SPTF) LASER VS HIGH POWER HO:YAG LASER Caleb S Miller, Bristol B Whiles, David A Duchene, Donald A Neff, and Wilson R Molina Caleb S MillerCaleb S Miller More articles by this author , Bristol B WhilesBristol B Whiles More articles by this author , David A DucheneDavid A Duchene More articles by this author , Donald A NeffDonald A Neff More articles by this author , and Wilson R MolinaWilson R Molina More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002019.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Digital ureteroscopes employ “chip on the tip” technology which allows significant improvement in image resolution. However, image distortion often occurs during laser lithotripsy due to acoustic wave production. We sought to compare the Super Pulse Thulium Fiber (SPTF) laser with the high power Holmium (Ho:YAG) laser in terms of image distortion using variable laser power settings and laser fiber tip distance from the scope’s tip. METHODS: Utilizing a silicone renal model fitted with a 12/14F access sheath, we developed a laboratory model to simulate ureteroscopy. The LithoVue (Boston Scientific), disposable digital flexible ureteroscope was used with 200 micron laser fibers for both the SPTF (Soltive-Olympus) and High power Ho:YAG laser (P120-Lumenis). At defined laser parameters (10, 20, 30, and 40W; short pulse) the laser fiber was slowly retracted toward the tip of the scope during laser activation. Image distortion was identified, and distance from the laser tip to the scope tip was determined. Data from the two lasers were compared utilizing a paired t-test. RESULTS: Image distortion occurred at greater distance with the Ho:YAG compared to SPTF at all laser settings (Table 1). Additionally, higher power (W) was associated with image distortion occurring further from the tip of the scope (p<0.01 for Ho:YAG; p=0.02 for SPFT). At the same power (W) with either 1J or 0.5J, there was no difference in distance for image distortion for the Ho:YAG, but distortion occurred differently with the SPTF (20 and 40W; p<0.01 and p=0.02, respectively). CONCLUSIONS: Increased total power as well as decreased distance between the scope and laser fiber tip results in image distortion during flexible ureteroscopy. Image distortion occurs at a greater distance with the Ho:YAG laser than with SPTF fibers at the same laser settings. SPTF seems to have a better safety profile in terms image distortion and potential scope damage. Further evaluation utilizing Ho:YAG on modulated pulse mode is warranted. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e440-e440 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Caleb S Miller More articles by this author Bristol B Whiles More articles by this author David A Duchene More articles by this author Donald A Neff More articles by this author Wilson R Molina More articles by this author Expand All Advertisement Loading ...

PD54-08 HOLMIUM:YAG (HO:YAG) VERSUS THULIUM FIBER LASER (TFL) FOR TREATMENT OF UPPER URINARY TRACT CALCULI IN DUSTING MODE: A CLINICAL COMPARISON OF EFFICIENCY, EFFICACY AND COSTS EFFECTIVENESS

You have accessJournal of UrologyStone Disease: Surgical Therapy IV (PD54)1 Sep 2021PD54-08 HOLMIUM:YAG (HO:YAG) VERSUS THULIUM FIBER LASER (TFL) FOR TREATMENT OF UPPER URINARY TRACT CALCULI IN DUSTING MODE: A CLINICAL COMPARISON OF EFFICIENCY, EFFICACY AND COSTS EFFECTIVENESS Ahmed Ghazi, Mahmoud Khalil, Changyong Feng, Scott Quarrier, and Rajat Jain Ahmed GhaziAhmed Ghazi More articles by this author , Mahmoud KhalilMahmoud Khalil More articles by this author , Changyong FengChangyong Feng More articles by this author , Scott QuarrierScott Quarrier More articles by this author , and Rajat JainRajat Jain More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002081.08AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Preliminary studies have demonstrated the superiority of TFL compared to Ho:YAG for dusting of urinary calculi. These are mainly based on laboratory studies with emerging clinical reports limited to optimizing TFL dusting settings. We aim to compare the efficiency, effectiveness and costs effectiveness of high power Ho:YAG (100W Empower, Olympus) to TFL (Soltive PLS, Olympus) lasers operated at a fixed dusting protocol. METHODS: A prospective study of 62 patients (31 per group) with 10–30 mm renal calculi was completed. Fixed dusting settings (0.4J X 60Hz) during retrograde intrarenal surgery (RIRS) lithotripsy was used for both lasers. Laser on time (LOT), Ablation efficacy (J/mm3) and Ablation speed (mm3/second) were calculated. Retropulsion, visibility, and bleeding during RIRS were graded by 3 urologists using 5-point Likert scales. Stone-free rate (SFR) was assessed at 1 month with non-contrast CT. Projected cost savings were calculated utilizing the formula [average LOT difference x $100/minute billed to insurance for RIRS minus $178 differential between list price of the 200m TFL ball tip and regular Ho:YAG fiber plus price differential for upgrade to PLS Soltive ($18800/1000) amortized over 1000 procedures=$18.8]. RESULTS: Mean age, BMI, stone number, density, ellipsoid stone volume and STONE score was not significantly different among both groups (Table 1). TFL lithotripsy had significantly shorter LOTs (380.6 vs 533.6 seconds, p=0.015) and higher SFRs (68% vs 34.8%, p=0.03). Both ablation efficacy (21.2 vs 12.5 J/mm3, p=0.02) and speed (4.1 vs 1.2 mm3/second, p=0.003) were significantly higher with TFL. TFL was 2.6 min faster for all stones (3.4 min for stones <15mm vs 1.7min for stones >15mm) with an overall projected $69.2 saving per case [$266- ($178+ $18.8) (Table 1). TFL was superior in terms of retropulsion (1.6 vs 2.8), visibility (1.8 vs 3.3) and bleeding (1.1 vs 1.9) gradings. CONCLUSIONS: This clinical study demonstrates TFL as a more effective, efficient and cost effective laser during RIRS lithotripsy when operated in dusting mode, producing higher stone ablation rates and speed with improved stone free rates than Ho:YAG laser. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e925-e926 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ahmed Ghazi More articles by this author Mahmoud Khalil More articles by this author Changyong Feng More articles by this author Scott Quarrier More articles by this author Rajat Jain More articles by this author Expand All Advertisement Loading ...

Low-energy high-frequency Ho-YAG lithotripsy: is RIRS going forward? A case-control study.

Retrograde Intra-Renal Surgery (RIRS) plays a primary role in renal stone treatment context. Energy, frequency and width of laser impulse can be modulated by surgeons to achieve better outcomes. In our study, patients with single renal stone sized 10-20mm were retrospectively divided into two groups. Patients of Group 1 underwent RIRS with Low-Energy (LE) High-Frequency (HF) settings using Lumenis® 120-W high-power Ho:YAG laser. Patients of Group 2 (control) underwent RIRS using "standard" settings by means of Sphinx® Jr 30W Ho:YAG system. Follow-up was conducted with a CT scan at 3months after RIRS in both groups. Procedure success was defined as stone-free or presence of ≤ 4mm fragments (Clinical Insignificant Residual Fragments-CIRF). A total number of 199 patients were included: 86 LE/HF RIRS (Group 1) vs 113 "conventional" RIRS (Group 2). Mean operative time was 56.6 (± 19.4) min in Group 1 vs 65.2 (± 25.2) min in Group 2 (p = 0.01). Mean hospitalization time was 2.5 ± 1.7days for Group 1 vs 2.9 ± 3.2days for Group 2 (p = 0.2). Peri-operative complications were counted: eight in Group 1 and 11 in Group 2 (p > 0.05). At 3-month control, stone-free rate was 69% (59/86 patients) in Group 1 vs 65% (73/113 patients) in Group 2 (p = 0.6). Success rate was 93% (80/86) in Group 1 in comparison to 82% (93/113) in Group 2 (p = 0.03). In conclusion, LE/HF RIRS seems to be a feasible and effective technique with a reduction of operative time and optimal results in terms of "stone-free" and "success" rates. Further studies are needed to ensure the validity of our results and to give evidence-based statements.

High-power, High-frequency Ho:YAG Lasers Are Not Essential for Retrograde Intrarenal Surgery

There is currently insufficient in vivo evidence that high-power Ho:YAG lasers improve retrograde intrarenal surgery or the ablation efficacy. While prospective trials are awaited, a low-cost, silent, low-power Ho:YAG laser that requires only a standard electrical outlet is more than sufficient for retrograde intrarenal surgery.

Effects of irrigation parameters and access sheath size on the intra-renal temperature during flexible ureteroscopy with a high-power laser.

To investigate the effect of different laser power settings on intra-renal temperature (IRT) under different irrigation conditions during flexible ureteroscopy (FURS) in a live-anesthetized porcine model. Following ethics approval, 2 female pigs weighing ~ 28kg were used. Under general anesthesia, a percutaneous access was obtained to fix a K-type thermocouple inside the pelvi-calyceal system for real-time recording of IRT during FURS without UAS, UAS-10/12, UAS-12/14, and UAS-14/16F. A high-power holmium laser was used and the IRT was recorded during laser activation for up to 60s at a laser power of 20W, 40W, and 60W under gravity irrigation and manual pump irrigation. Under gravity irrigation, FURS without UAS was associated with hazardous IRT at a laser power as low as 20W for as short as 20s of laser activation. The IRT was rendered borderline when UAS was used. This UAS buffering effect disappeared with the use of higher laser-power settings (40W and 60W) with the maximal IRT exceeding 60°C. Moreover, laser activation at 60W was associated with very rapid increase in IRT within few seconds. Under pump irrigation, laser activation at the highest power setting (60W) for 60s was associated with a safe IRT, even without the use of UAS. The maximal IRT was below 45°C. The use of high-power Ho:YAG laser carries potentially harmful thermal effect when used under gravity irrigation, even when large-diameter UAS is used. High-power settings (> 40W) require high irrigation flow. The use of UAS is advisable to reduce the IRT and balance any intra-renal pressure increase.

High Power Ho:YAP Laser With 107 W of Output Power at 2117 nm

A high power Ho:YAP laser in-band pumped by a home-constructed Tm doped all fiber master oscillator power amplifier (MOPA) is reported. The optically polished and uncoated Ho:YAP laser yielded over 107 W of output power at ~2117.1 nm with 215.4 W of absorbed pump power, corresponding to a slope efficiency of 50.6% with respect to the absorbed pump power. The beam quality M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> parameter was measured at 80 W of output power to be ~3.2 and ~2.6 in x- and y-directions, respectively.

Lasers for stone treatment: how safe are they?

To update laser lithotripsy advances in regard to new laser types and technologies as well as review contemporary laser safety concerns. The high prevalence of urolithiasis and the continuing miniaturization of scopes has encouraged the growth of laser lithotripsy technology. The holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been used for over 20 years in endourology and has been extensively studied. Holmium laser power output is affected by a number of factors, including pulse energy, pulse frequency, and pulse width. Several recent experimental studies suggest that the new dual-phase Moses 'pulse modulation' technology, introduced in high-power laser machines, carries a potential to increase stone ablation efficiency and decrease stone retropulsion. A newly introduced thulium fiber laser (TFL) has been adapted to a very small laser fiber size and is able to generate very low pulse energy and very high pulse frequency. Both of these technologies promise to play a larger role in laser lithotripsy in the near future. However, more experimental and clinical studies are needed to expand on these early experimental findings. Even though laser lithotripsy is considered safe, precautions should be taken to avoid harmful or even catastrophic adverse events to the patient or the operating room staff. The Ho:YAG laser remains the clinical gold standard for laser lithotripsy for over the last two decades. High-power Ho:YAG laser machines with Moses technology have the potential to decrease stone retropulsion and enhance efficiency of laser ablation. The new TFL has a potential to compete with and perhaps even replace the Ho:YAG laser for laser lithotripsy. Safety precautions should be taken into consideration during laser lithotripsy.

35 W continuous-wave Ho:YAG single-crystal fiber laser

We report on a high-power Ho:YAG single-crystal fiber (SCF) laser inband pumped by a high-brightness Tm-fiber laser at 1908 nm. The Ho:YAG SCF grown by the micro-pulling-down technique exhibits a propagation loss of $0.05\pm 0.005~\text{cm}^{-1}$ at $2.09~\unicode[STIX]{x03BC}\text{m}$ . A continuous-wave output power of 35.2 W is achieved with a slope efficiency of 42.7%, which is to the best of our knowledge the highest power ever reported from an SCF-based laser in the 2 $\unicode[STIX]{x03BC}\text{m}$ spectral range.

A 142 W Ho:YAG laser single-end-pumped by a Tm-doped fiber laser at 1931 nm

In this paper, a high-power Ho:YAG laser in-band pumped by a Tm-doped fiber laser at 1931 nm is reported. A maximum output power of 142.2 W is achieved at 2091 nm using a single-end-pumped configuration, corresponding to a slope efficiency of 56.7%. This is, to the best of our knowledge, the highest output power directly generated by bulk Ho-oscillators in the 2.1 µm spectral region.

The laser of the future: reality and expectations about the new thulium fiber laser-a systematic review.

The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been the gold-standard for laser lithotripsy over the last 20 years. However, recent reports about a new prototype thulium fiber laser (TFL) lithotripter have revealed impressive levels of performance. We therefore decided to systematically review the reality and expectations for this new TFL technology. This review was registered in the PROSPERO registry (CRD42019128695). A PubMed search was performed for papers including specific terms relevant to this systematic review published between the years 2015 and 2019, including already accepted but not yet published papers. Additionally, the medical sections of ScienceDirect, Wiley, SpringerLink, Mary Ann Liebert publishers, and Google Scholar were also searched for peer-reviewed abstract presentations. All relevant studies and data identified in the bibliographic search were selected, categorized, and summarized. The authors adhered to PRISMA guidelines for this review. The TFL emits laser radiation at a wavelength of 1,940 nm, and has an optical penetration depth in water about four-times shorter than the Ho:YAG laser. This results in four-times lower stone ablation thresholds, as well as lower tissue ablation thresholds. As the TFL uses electronically-modulated laser diodes, it offers the most comprehensive and flexible range of laser parameters among laser lithotripters, with pulse frequencies up to 2,200 Hz, very low to very high pulse energies (0.005-6 J), short to very long-pulse durations (200 µs up to 12 ms), and a total power level up to 55 W. The stone ablation efficiency is up to four-times that of the Ho:YAG laser for similar laser parameters, with associated implications for speed and operating time. When using dusting settings, the TFL outperforms the Ho:YAG laser in dust quantity and quality, producing much finer particles. Retropulsion is also significantly reduced and sometimes even absent with the TFL. The TFL can use small laser fibers (as small as 50 µm core), with resulting advantages in irrigation, scope deflection, retropulsion reduction, and (in)direct effects on accessibility, visibility, efficiency, and surgical time, as well as offering future miniaturization possibilities. Similar to the Ho:YAG laser, the TFL can also be used for soft tissue applications such as prostate enucleation (ThuFLEP). The TFL machine itself is seven times smaller and eight times lighter than a high-power Ho:YAG laser system, and consumes nine times less energy. Maintenance is expected to be very low due to the durability of its components. The safety profile is also better in many aspects, i.e., for patients, instruments, and surgeons. The advantages of the TFL over the Ho:YAG laser are simply too extensive to be ignored. The TFL appears to be a real alternative to the Ho:YAG laser and become a true game-changer in laser lithotripsy. Due to its novelty, further studies are needed to broaden our understanding of the TFL, and comprehend the full implications and benefits of this new technology, as well its limitations.

High power Ho:SSO laser resonantly pumped by a FBG-locked Tm fiber laser at 1940.3 nm

We demonstrate a high power continuous wave Ho:SSO laser resonantly pumped by a FBG-locked Tm fiber laser at 1940.3nm in this paper. The maximum output power of 8.72W was obtained under the incident pump power of 19.8W, corresponding to a slope efficiency of 54.3% and an optical conversion efficiency of 44.0%. The output wavelength of Ho:SSO laser was centered at 2113.5 nm. The Ho:SSO laser operated at TEM00 mode with a beam quality factor of Mx2 of 1.6 and My2 of 1.4 at maximum output level.