High-brightness scalable continuous-wave single-mode photonic-crystal laser.

Realizing large-scale single-mode, high-power, high-beam-quality semiconductor lasers, which rival (or even replace) bulky gas and solid-state lasers, is one of the ultimate goals of photonics and laser physics. Conventional high-power semiconductor lasers, however, inevitably suffer from poor beam quality owing to the onset of many-mode oscillation1,2, and, moreover, the oscillation is destabilized by disruptive thermal effects under continuous-wave (CW) operation3,4. Here, we surmount these challenges by developing large-scale photonic-crystal surface-emitting lasers with controlled Hermitian and non-Hermitian couplings inside the photonic crystal and a pre-installed spatial distribution of the lattice constant, which maintains these couplings even under CW conditions. A CW output power exceeding 50 W with purely single-mode oscillation and an exceptionally narrow beam divergence of 0.05° has been achieved for photonic-crystal surface-emitting lasers with a large resonant diameter of 3 mm, corresponding to over 10,000 wavelengths in the material. The brightness, a figure of merit encapsulating both output power and beam quality, reaches 1 GW cm-2 sr-1, which rivals those of existing bulky lasers. Our work is an important milestone toward the advent of single-mode 1-kW-class semiconductor lasers, which are expected to replace conventional, bulkier lasers in the near future.

Evolutionary histories of breast cancer and related clones.

Recent studies have documented frequent evolution of clones carrying common cancer mutations in apparently normal tissues, which are implicated in cancer development1-3. However, our knowledge is still missing with regard to what additional driver events take place in what order, before one or more of these clones in normal tissues ultimately evolve to cancer. Here, using phylogenetic analyses of multiple microdissected samples from both cancer and non-cancer lesions, we show unique evolutionary histories of breast cancers harbouring der(1;16), a common driver alteration found in roughly 20% of breast cancers. The approximate timing of early evolutionary events was estimated from the mutation rate measured in normal epithelial cells. In der(1;16)(+) cancers, the derivative chromosome was acquired from early puberty to late adolescence, followed by the emergence of a common ancestor by the patient's early 30s, from which both cancer and non-cancer clones evolved. Replacing the pre-existing mammary epithelium in the following years, these clones occupied a large area within the premenopausal breast tissues by the time of cancer diagnosis. Evolution of multiple independent cancer founders from the non-cancer ancestors was common, contributing to intratumour heterogeneity. The number of driver events did not correlate with histology, suggesting the role of local microenvironments and/or epigenetic driver events. A similar evolutionary pattern was also observed in another case evolving from an AKT1-mutated founder. Taken together, our findings provide new insight into how breast cancer evolves.

High-power and high-efficiency operation of 1.3 µm-wavelength InP-based photonic-crystal surface-emitting lasers with metal reflector.

We demonstrate high-output-power and high-efficiency operation of 1.3-µm-wavelength InP-based photonic-crystal surface-emitting lasers (PCSELs). By introducing a metal reflector and adjusting the phase of the reflected light via optimization of the thickness of the p-InP cladding layer, we successfully achieve an output power of approximately 400 mW with the slope efficiency of 0.4 W/A and the wall-plug efficiency of 20% under CW conditions. In addition, this PCSEL exhibits a narrow circular beam with a divergence angle below 1.6° even at high output powers under CW conditions at temperatures from 15°C to 50°C. We have also demonstrated an output power of over 12 W under pulsed conditions at room temperature.

A machine learning model for predicting the lymph node metastasis of early gastric cancer not meeting the endoscopic curability criteria.

BACKGROUND: We developed a machine learning (ML) model to predict the risk of lymph node metastasis (LNM) in patients with early gastric cancer (EGC) who did not meet the existing Japanese endoscopic curability criteria and compared its performance with that of the most common clinical risk scoring system, the eCura system. METHODS: We used data from 4,042 consecutive patients with EGC from 21 institutions who underwent endoscopic submucosal dissection (ESD) and/or surgery between 2010 and 2021. All resected EGCs were histologically confirmed not to satisfy the current Japanese endoscopic curability criteria. Of all patients, 3,506 constituted the training cohort to develop the neural network-based ML model, and 536 constituted the validation cohort. The performance of our ML model, as measured by the area under the receiver operating characteristic curve (AUC), was compared with that of the eCura system in the validation cohort. RESULTS: LNM rates were 14% (503/3,506) and 7% (39/536) in the training and validation cohorts, respectively. The ML model identified patients with LNM with an AUC of 0.83 (95% confidence interval, 0.76-0.89) in the validation cohort, while the eCura system identified patients with LNM with an AUC of 0.77 (95% confidence interval, 0.70-0.85) (P = 0.006, DeLong's test). CONCLUSIONS: Our ML model performed better than the eCura system for predicting LNM risk in patients with EGC who did not meet the existing Japanese endoscopic curability criteria. We developed a neural network-based machine learning model that predicts the risk of lymph node metastasis in patients with early gastric cancer who did not meet the endoscopic curability criteria.

Endoscopic Features of Synchronous Multiple Early Gastric Cancers: Findings from a Nationwide Cohort.

INTRODUCTION: We investigated the factors associated with synchronous multiple early gastric cancers and determined their localization. METHODS: We analyzed 8,191 patients who underwent endoscopic submucosal dissection for early gastric cancers at 33 hospitals in Japan from November 2013 to October 2016. Background factors were compared between single-lesion (n = 7,221) and synchronous multi-lesion cases (n = 970) using univariate and multivariate analyses. We extracted cases with two synchronous lesions (n = 832) and evaluated their localization. RESULTS: Significant independent risk factors for synchronous multiple early gastric cancer were older age (≥75 years old) (odds ratio [OR] = 1.257), male sex (OR = 1.385), severe mucosal atrophy (OR = 1.400), tumor localization in the middle (OR = 1.362) or lower region (OR = 1.404), and submucosal invasion (OR = 1.528 [SM1], 1.488 [SM2]). Depressed macroscopic type (OR = 0.679) and pure undifferentiated histology OR = 0.334) were more common in single early gastric cancers. When one lesion was in the upper region, the other was more frequently located in the lesser curvature of the middle region. When one lesion was in the middle region, the other was more frequently located in the middle region or the lesser curvature of the lower region. When one lesion was in the lower region, the other was more frequently located in the lesser curvature of the middle region or the lower region. CONCLUSION: Factors associated with synchronous multiple early gastric cancer included older age, male sex, severe mucosal atrophy, tumor localization in the middle or lower region, and tumor submucosal invasion. Our findings provide useful information regarding specific areas that should be examined carefully when one lesion is detected.

Association between the Prognostic Nutritional Index and the Occurrence of Immune-Related Adverse Events.

Immune-related adverse events (irAEs) affect all organs and are associated with various symptoms. The identification of biomarkers that can predict irAEs may be particularly clinically useful. This study aimed to investigate whether the prognostic nutritional index (PNI) before the initiation of immune checkpoint inhibitor (ICI) treatment can predict the occurrence of irAEs. We conducted a survey of 111 patients with cancer who were receiving ICI fixed-dose monotherapy at Saga University Hospital from the time each ICI became available until January 2020. We compared the PNI between the patients with and without irAE expression, established a cutoff value for PNI associated with the development of irAEs, and investigated the incidence of irAEs and progression-free survival (PFS) in groups divided by the cutoff value. Patients with irAEs had significantly higher PNI than did those without, and there was a significant association between PNI and irAEs after adjusting for potential factors (odds ratio, 1.12; 95% confidence interval, 1.03-1.21). In addition, PNI ≥44.2 was associated with a significantly higher incidence of irAEs (75.0% vs. 35.2%, p = 0.0001) and significantly longer PFS than PNI <44.2 (p = 0.025). In conclusion, pretreatment PNI may be associated with the risk of developing irAEs in patients with advanced recurrent solid tumors. When the PNI is ≥44.2, patient management is important for avoiding serious AEs because while the treatment may be effective, the occurrence of irAEs is a concern.

Efficacy and Safety of Re-administration of Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitor (EGFR-TKI) After EGFR-TKI-Induced Interstitial Lung Disease (CS-Lung-005).

PURPOSE: This study investigated the safety and efficacy of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) re-administration after recovery from EGFR-TKI-induced interstitial lung disease (ILD). METHODS: This multicenter retrospective study collected data from consecutive advanced NSCLC patients who underwent EGFR-TKI re-administration after recovery from EGFR-TKI-induced ILD. RESULTS: Fifty-eight patients were registered. The grades of initial TKI-induced ILD were grade 1 to 4. TKIs used for re-administration were erlotinib for 15 patients, osimertinib for 15, gefitinib for 14, afatinib for 13 patients, and dacomitinib for 1 patient. ILD recurred in 13 patients (22.4%), comprising 3 patients with grade 1, 6 patients with grade 2, and 4 patients with grade 3. No significant associations were found between ILD recurrence and age, smoking history, performance status, time from initial ILD to TKI re-administration, or concomitant corticosteroid use. However, the incidence of ILD recurrence was high in cases of repeated use of gefitinib or erlotinib or first time use of osimertinib at TKI re-administration. The ILD recurrence rate was lowest in patients treated with first time use of gefitinib (8%) or erlotinib (8%), followed by patients treated with repeated use of osimertinib (9%). The response rate, median progression-free survival by TKI re-administration, and median overall survival were 55%, 9.6 and 84.8 months, respectively. CONCLUSION: This study showed that EGFR-TKI re-administration is a feasible and effective treatment for patients who recovered from EGFR-TKI-induced ILD. Our results indicate that re-administration of EGFR-TKI is an important option for long-term prognosis after recovery from EGFR-TKI-induced ILD.

Relationships between Type 1 interferon signatures and clinical features of the new-onset lupus patients in Japan.

OBJECTIVES: The objective of the study is to investigate the relationships between Type 1 interferon (T1-IFN) signatures and clinical characteristics of lupus patients. METHODS: We examined 49 new-onset lupus patients who were diagnosed between 1999 and 2017. The patients treated with >10 mg of prednisolone or hydroxychloroquine were excluded from this study. Serum T1-IFN signatures were revealed by a functional reporter assay and standardized by recombinant IFN-α. Patient backgrounds, clinical findings, and treatments were retrospectively extracted from their electrical medical records. Clinical data were also available, including SLE Disease Activity Index of SLE patients on admission. RESULTS: T1-IFN signatures of lupus patients closely correlated with lupus disease activities, such as SLE Disease Activity Index-2K, white blood cell, C3 levels, and the titre of double-strand DNA antibody. We found fever and acute lupus dermatitis closely associated with T1-IFN signature. CONCLUSIONS: In lupus patients, fever and acute lupus dermatitis are good indicators of a strong T1-IFN signature.

[Ascending Colon Cancer with Radical Resection after Stent Reimplantation Due to Colonic Stent Obstruction for Palliation-A Case Report].

Since the insurance coverage of colorectal stents for bowel obstruction due to colorectal cancer in 2012, the use of colorectal stenting for palliation has rapidly spread. We report a case of ascending colon cancer in which a colorectal stent was placed for palliation, but the stent was reimplanted due to obstruction, followed by radical resection. The patient was a 92- year-old woman who was brought to the emergency room at the age of 90 years with repeated vomiting and abdominal pain, and was diagnosed as colorectal cancer ileus caused by ascending colon cancer, and a colorectal stent was inserted. She received palliative care and had been asymptomatic for 1 year and 3 months, but due to in-stent stenosis, she had bowel obstruction and sent to emergency room, and another stent was installed. The patient had a good course, but 4 months after the second stenting, she was concerned about restenosis and referred to the department of surgery, then performed a radical resection. The indication for colorectal stents for palliative purposes should be considered on a case-by- case basis, including ADL, stage of the disease, and prognosis.

200-W short-pulse operation of photonic-crystal lasers based on simultaneous absorptive and radiative Q-switching.

Short-pulse high-peak-power lasers are crucial laser sources for various applications such as non-thermal ultrafine material processing and eye-safe high-resolution remote sensing. Realizing such operation in a single semiconductor laser chip without amplifiers or external resonators is expected to contribute to the development of compact, affordable laser sources for such applications. In this paper, we demonstrate short-pulse high-peak-power photonic-crystal surface-emitting lasers based on simultaneous absorptive and radiative Q-switching. The proposed device induces an instantaneous and simultaneous decrease in both absorptive and out-of-plane radiation losses due to saturable absorption and self-evolution of the photonic band, respectively, which results in drastic Q-switching operation of the device. Based on this concept, we experimentally demonstrate short-pulse generation with 200-W-class peak power and a pulse width of < 30 ps. In addition, via pulse compression with dispersion compensation, we achieve an even higher peak power of ∼300 W with a shorter pulse width of ∼10 ps.

Topological Unidirectional Guided Resonances Emerged from Interband Coupling.

Unidirectional guided resonances (UGRs) are optical modes in photonic crystal slabs that radiate toward one side without the need for mirrors on the other. In this Letter, we report a mechanism to realize UGRs by tuning the interband coupling effect originating from up-down symmetry breaking. We theoretically find that UGRs that reside along high-symmetric lines correspond to phase singularities of far-field radiation, depicted by phase winding numbers as a type of topological indices. We investigate the phase dislocation lines in three-dimensional parameter space and elaborate on the interplay between UGRs and non-Hermitian degeneracies accordingly. Our findings reveal the topological nature of UGRs about their generation, evolution, and annihilation in general parameter spaces, thus paving the way to new possibilities of light manipulation.

Association between perioperative management of antiplatelet agents and risk of post-endoscopic submucosal dissection bleeding in early gastric cancer: analysis of a nationwide multicenter study.

BACKGROUND AND AIMS: Data are lacking regarding post-endoscopic submucosal dissection (ESD) bleeding in patients with early gastric cancer (EGC) who take antiplatelet agents (APAs), particularly in those taking thienopyridine and cilostazol. We aimed to clarify the association between the status of APA medication and post-ESD bleeding risk. METHODS: This study is a secondary analysis using data from a recently conducted nationwide multicenter study in Japan. We retrospectively reviewed patients treated with APAs or on no antithrombotic therapy recruited from 33 institutions who underwent ESD for EGC between November 2013 and October 2016. The primary outcome of this study was the relationship between the rate of post-ESD bleeding and the status of each APA medication. RESULTS: A total of 9736 patients were included in the analysis. Among 665 aspirin users, the continuation group was significantly associated with post-ESD bleeding (odds ratio [OR], 2.79; 95% confidence interval [CI], 1.77-4.37). Among 227 thienopyridine users, the aspirin or cilostazol replacement group was not significantly associated with post-ESD bleeding (OR, 1.85; 95% CI, .72-4.78). Among 158 cilostazol users, there was no significant association with post-ESD bleeding, irrespective of medication status. The rate of post-ESD bleeding was approximately 10% to 20% irrespective of the status of APA administration among dual-antiplatelet therapy users. No patients experienced thromboembolic events in this study. CONCLUSIONS: Replacement of thienopyridine with aspirin or cilostazol may be acceptable for minimizing both the risk of post-ESD bleeding and thromboembolism in patients with EGC. In patients on cilostazol monotherapy undergoing ESD, continuation of therapy may be acceptable.

Endoscopic features and clinical course of colorectal carcinoma resected by cold snare polypectomy.

BACKGROUND AND AIM: Cold snare polypectomy is commonly performed to remove small colorectal polyps. Accidental resection of carcinomas during this procedure has been reported. Herein, we aimed to clarify the clinicopathological features and clinical course of colorectal carcinomas resected by cold snare polypectomy. METHODS: This multicenter retrospective cohort study was conducted at 10 Japanese healthcare centers. Of the colorectal lesions resected by cold snare polypectomy between April 2016 and March 2020, lesions pathologically diagnosed as carcinoma were reviewed. Centralized histology (based on the Vienna classification) and endoscopic reviews were performed. The study endpoints were endoscopic features and clinical outcomes of cold snare polypectomy-resected colorectal carcinomas (Vienna category ≥4.2). RESULTS: We reviewed 74 of the 70 693 lesions resected by cold snare polypectomy. After a central pathological review, 68 lesions were diagnosed as carcinomas. The Japan Narrow-band imaging Expert Team (JNET) classification type 2B, lesion size ≥6 mm, and multinodular morphology were the significant endoscopic predictors of carcinoma resected by cold snare polypectomy. No adverse events related to the procedure occurred. Sixty-three lesions were diagnosed as carcinomas within the mucosal layer, and 34 were curative resections. Of the five carcinoma lesions with submucosal invasion, additional surgery revealed remnant cancer tissues in one lesion. No local or metastatic recurrence was observed during follow-up. CONCLUSIONS: Although most of the carcinomas resected by cold snare polypectomy were within the mucosal layer, few lesions invading the submucosa were identified. Careful pre-procedural endoscopic evaluation, especially focusing on the JNET classification and multinodular morphology, is recommended.

Diagnostic value of endoscopic ultrasonography for the depth of gastric cancer suspected of submucosal invasion: a multicenter prospective study.

BACKGROUND: Although the combination of conventional endoscopy (CE) and endoscopic ultrasonography (EUS) is useful for predicting the depth of early gastric cancer (EGC), the diagnostic value of EUS for submucosal (SM) invasive cancer has not been fully investigated. METHODS: We conducted a multicenter prospective study from May 2017 to January 2021 to evaluate the validity of a diagnostic strategy combining CE and EUS and to clarify the additional value of EUS for EGC suspected of SM invasion. In each case, the diagnosis was first made using CE, followed by EUS, and finally confirmed using a combination algorithm. RESULTS: A total of 180 patients with EGC were enrolled from 10 institutions, of which 175 were analyzed. The histopathological depths were M, SM1, SM2, and ≥ MP in 72, 16, 64, and 23 lesions, respectively. Treatment included 92 endoscopic submucosal dissection cases and 83 surgical cases. The overall diagnostic accuracy classified by M-SM1 or SM2-MP was 58.3% for CE, 75.7% for EUS, and 78.9% for the combination of CE and EUS; the latter two were significantly higher than that of CE alone (P < 0.001). The CE, EUS, and combination accuracy rates in 108 differentiated-type lesions were 51.9%, 77.4%, and 79.6%, respectively; the latter two were significantly higher than CE alone (P < 0.001). A significant additive effect of EUS was observed in CE-SM2 low-confidence lesions but not in CE-M-SM1 lesions or in CE-SM2 high-confidence lesions. Among the nine CE findings, irregular surface, submucosal tumor-like elevation, and non-extension signs were significant independent markers of pSM2-MP. Poorly delineated EUS lesions were misdiagnosed. CONCLUSIONS: EUS provides additional value for differentiated-type and CE-SM2 low-confidence EGCs in diagnosing invasion depth. CLINICAL REGISTRATION NUMBER: UMIN000025862.

[A Case of Refractory Lymphorrhea after Laparoscopic Distal Gastrectomy].

An 84-year-old man with gastric cancer, cT2N0M0, cStage Ⅰ underwent laparoscopic distal gastrectomy, D1+dissection, and Roux-en-Y reconstruction. We started enteral nutrition on the second postoperative day, but milky drainage appeared from the drain on the fifth postoperative day. The triglyceride in the ascites was markedly elevated, and it was diagnosed as a lymphorrhea. Neither conservative treatment nor lymphangiography were successful. We decided to perform surgical intervention because the lymphorrhea did not improve for about 1 month after gastrectomy. At laparotomy, we detected the lymphatic ducts using enteral nutrition of fat formulas during surgery and successfully closed the lymphatic ducts by suturing and ligation on the 38th postoperative day. Prolonged lymphorrhea causes extreme deterioration of the patient's general condition. Prolonged total parenteral nutrition also increases the risk of infection. It is important to perform surgical treatment for intractable lymphorrhea that does not improve with conservative treatment without hesitation.

Nonrecurrence Rate of Underwater EMR for ≤20-mm Nonampullary Duodenal Adenomas: A Multicenter Prospective Study (D-UEMR Study).

BACKGROUND AND AIMS: Endoscopic resection of nonampullary duodenal adenoma is often challenging, and its technique has not yet been standardized. To overcome the practical difficulty of conventional endoscopic mucosal resection, underwater endoscopic mucosal resection (UEMR) was recently developed; therefore, we investigated the effectiveness and safety of UEMR for nonampullary duodenal adenoma. METHODS: A multicenter, prospective cohort study was conducted at 21 institutions in Japan. We enrolled patients with no more than 2 nonampullary duodenal adenomas ≤20 mm in size, who were planned to undergo UEMR. After UEMR, follow-up endoscopies were scheduled at 2 and 12 months after the procedure, and biopsy specimens were taken from the post-UEMR scars. The primary endpoint was the proportion of patients with histologically proven nonrecurrence at follow-up endoscopy and biopsy. RESULTS: A total of 155 patients with 166 lesions underwent UEMR. One patient with a non-neoplastic lesion in the resected specimen and 10 patients with 10 lesions who were lost to follow-up were excluded. Finally, 144 patients with 155 lesions who received all follow-up endoscopies were analyzed for the primary endpoint. The proportion of patients with proven nonrecurrence was 97.2% (n = 140 of 144; 95% confidence interval, 92.8%-99.1%) which exceeded the predefined threshold value (92%). Two cases of delayed bleeding (1.2%) occurred and they were successfully managed by clips. All recurrences were successfully treated by additional endoscopic treatment. CONCLUSIONS: This multicenter, prospective cohort study demonstrated effectiveness and safety of UEMR for nonampullary duodenal adenomas ≤20 mm in size. (University Hospital Medical Network Clinical Trials Registry, Number: UMIN000030414).

The clinical significance of tertiary lymphoid structure and its relationship with peripheral blood characteristics in patients with surgically resected non-small cell lung cancer: a single-center, retrospective study.

INTRODUCTION: The presence of tertiary lymphoid structure (TLS) in tumor tissues has been reported to be a factor associated with a good prognosis in several types of cancers. However, the relationship between TLS formation and peripheral blood findings remains unclear. The purposes of the study were to evaluate the effect of the presence of TLS on survival and determine the peripheral blood characteristics associated with TLS formation in non-small cell lung cancer (NSCLC) patients. METHODS: A total of 147 consecutive NSCLC patients who underwent lung resection at Fukushima Medical University Hospital between 2013 and 2017 were enrolled. TLS expression was evaluated, and the relationships between clinical parameters and outcomes were analyzed. Peripheral blood mononuclear cells (PBMCs) were further analyzed by mass cytometry to characterize the TLS-positive microenvironment. RESULTS: Forty-six patients had high TLS expression, and the remaining 101 patients had low TLS expression. In stage II to IV patients (n = 35), disease-free survival was longer in the high TLS expression group (p = 0.027). A low neutrophil to lymphocyte ratio (NLR) < 2.75 in the peripheral blood was associated with high TLS expression (p = 0.003). Citrus analysis after mass cytometry assay showed that the number of cells expressing HLA-DR and CD9 in PBMCs was lower in the high TLS expression group. CONCLUSION: High TLS expression is associated with a good prognosis after surgery in stage II and III NSCLC patients. In the peripheral blood, a low NLR and few antigen-presenting cells indicate the presence of TLS in the tumor microenvironment.

Towards optimization of photonic-crystal surface-emitting lasers via quantum annealing.

Photonic-crystal surface-emitting lasers (PCSELs), which utilize a two-dimensional (2D) optical resonance inside a photonic crystal for lasing, feature various outstanding functionalities such as single-mode high-power operation and arbitrary control of beam polarizations. Although most of the previous designs of PCSELs employ spatially uniform photonic crystals, it is expected that lasing performance can be further improved if it becomes possible to optimize the spatial distribution of photonic crystals. In this paper, we investigate the structural optimization of PCSELs via quantum annealing towards high-power, narrow-beam-divergence operation with linear polarization. The optimization of PCSELs is performed by the iteration of the following three steps: (1) time-dependent 3D coupled-wave analysis of lasing performance, (2) formulation of the lasing performance via a factorization machine, and (3) selection of optimal solution(s) via quantum annealing. By using this approach, we discover an advanced PCSEL with a non-uniform spatial distribution of the band-edge frequency and injection current, which simultaneously enables higher output power, a narrower divergence angle, and a higher linear polarization ratio than conventional uniform PCSELs. Our results potentially indicate the universal applicability of quantum annealing, which has been mainly applied to specific types of discrete optimization problems so far, for various physics and engineering problems in the field of smart manufacturing.

Dually modulated photonic crystal lasers for wide-range flash illumination.

Flash light sources with a wide field of view (FOV) are indispensable in various fields such as light detection and ranging (LiDAR), optical wireless communication, and adaptive lighting. However, conventional flash light sources, which combine lasers with external optical elements, tend to suffer from high complexity, large size, and high cost. In this study, we investigate a new wide-FOV flash light source which does not require external optical elements, based on a dually modulated photonic crystal surface-emitting laser (PCSEL). First, we propose and design the concept of a photonic crystal into which information of gradually varying diffraction vectors is introduced in order to artificially broaden the divergence angle. We then experimentally demonstrate photonic crystals based on this concept. Finally, by arraying 100 such lasers with mutually different central emission angles and driving all of these lasers simultaneously, we successfully achieve optics-free, 4-W flash illumination over a FOV of 30° × 30° at a wavelength of 940 nm.

High-power CW oscillation of 1.3-µm wavelength InP-based photonic-crystal surface-emitting lasers.

We demonstrate high-power continuous-wave (CW) lasing oscillation of 1.3-µm wavelength InP-based photonic-crystal surface-emitting lasers (PCSELs). Single-mode operation with an output power of over 100 mW, a side-mode suppression ratio (SMSR) of over 50 dB, and a narrow single-lobe beam with a divergence angle of below 1.2° are successfully achieved by using a double-lattice photonic crystal structure consisting of high-aspect-ratio deep air holes. The double lattice is designed to enhance both the in-plane optical feedback and the surface radiation effects in the photonic crystal. The coupling coefficients for 180 ∘, +90 ∘, and -90 ∘ diffractions are estimated from the measurements of the photonic band structure as κ1D = 417 cm-1, κ2D+ = 135 cm-1, and κ2D- = 65 cm-1, respectively. The stable single-mode, high-beam-quality operation is attributed to these large coupling coefficients introduced by the asymmetric double-lattice structure.