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1 Outline High-power, high-brightness Al-free active region tapered lasers at 915 nm N. Michel, I. Hassiaoui, M. Lecomte, O. Parillaud, M. Calligaro, M. Krakowski Alcatel-Thales III-V Lab, Route Départementale Palaiseau, France Acknowledgements: the support of the European Commission through h the IST project n 511-7, Acknowledgements: Y.Robert, M. Carbonnelle, C. Dernazeratian and L. Teisseire for excellent technical assistance Q8 Workshop CAM 7 July 6, p. 1

2 High-power, high-brightness Al-free active region tapered lasers at 915 nm Outline Introduction Brightness Laser structure Index-guided tapered lasers (IG1) Clarinet lasers Conclusions Q8 Workshop CAM 7 July 6, p.

3 Introduction Targeted Applications: Pumping of solid-state state lasers Pumping of Er or Er/Yb lasers and double cladding amplifiers: 975 nm and 915 nm Broad area laser Ridge Tapered laser High Power ~ 1 µm Highly multimode Few µm Low Power Single mode High beam quality Few tens of µm High Power Single mode High beam quality Q8 Workshop CAM 7 July 6, p. 3

4 What is Brightness? Case of a single emitter P( W) Brightness B = S( cm²). Ω( srd) P 1 = λ² M M // Beam propagation factor M M π = 1/ e² 1/ e² // 4λ w θ Fast axis : diffraction limited beam (M²^ ~ 1) π // // = w1/ e² θ Slow axis : 1 < M² < 1/ e² 4λ High P and Low M² // High B Q8 Workshop CAM 7 July 6, p. 4

5 What is Brightness? Case of a bars ^ // Beam shaping optics Optical fiber 1 1 BPPbar = BPP BPP// BPPfiber = φ fiber NA Condition for efficient coupling fiber Q8 Workshop CAM 7 July 6, p. 5

6 Case of a bars What is Brightness? Total emissive width q^ q // BPP w = θ diffraction limited beam BPP = Total emissive width // θ // we need a low q // Beam shaping optics N intermediary beams ' = BPP ' // = BPP// BPP N BPP / N High P and Low q // High B Q8 Workshop CAM 7 July 6, p. 6

7 Broad area lasers Internal parameters a i =.5 cm -1 h i = 86% J = 86 A/cm GG = 15 cm -1 Characteristic temperatures Large Optical Cavity (LOC) AlGaInP GaInP GaInAs 1QW GaInP AlGaInP T = 179 K T 1 = 57 K On mm as-cleaved BA laser () (hq,ext ) a int =.48 cm -1 h q,int = 86 % Ith (ma) 4 3 GG = 14.7 cm -1 J = 85.6 A/cm Length (cm) /L (cm -1 ) Q8 Workshop CAM 7 July 6, p. 7

8 Broad area lasers Power charactersistics Far-field profile (fast axis) Power (W) C Current (A) WP efficiency (%) Power (a.u.) AR/HR mm x1 µm I th = 411 ma h d = 1.5 W/A P max = 7 W θ^= 3 FWHM Theory q FWHM = 31. Exp. Theory Exp. q FWHM = Angle( ) Q8 Workshop CAM 7 July 6, p. 8

9 Broad area lasers Far-field profile (slow axis) Power (a.u.) W 9 FWHM 1.7 at 1/e Angle ( ) M = 15.3 at 1/e² M² ss = 17.1 B = 7.8 MW/cm²/sr/sr Q8 Workshop CAM 7 July 6, p. 9

10 Tapered lasers: IG1 Power characteristics () 1. 5 HR.5 mm < 1 Few tens of µm AR Optical Power (W) WP efficiency (%) Current (A) Temp. ( C) I th (ma) h d (W/A) R s (W) T ( C) P opt (mw) Current (ma) Lambda (nm) Near max. power Q8 Workshop CAM 7 July 6, p. 1

11 Beam profiles at 1W (slow axis) Near-field at waist Far-field Optical Power (a.u.) µm FWHM 19.8 µm at 1/e 1. W 1.5 A Optical Power (a.u.) at 1/e 6. FWHM 1. W 1.5 A Position (µm) Angle ( ) M at 1/e < 3. M ss < 3. Angle ~ 1 at 1/e at 1W Q8 Workshop CAM 7 July 6, p. 11

12 Tapered lasers: Clarinets Power characteristics ().8 4 HR.5 mm Few tens of µm AR Borruel et al. APL 87, p (5) Borruel et al. CLEO Europe 5, Paper CB6-4 Optical Power (W) Current (A) 3 1 WP efficiency (%) Temp. ( C) I th (ma) h d (W/A) R s (W) T ( C) P opt (mw) Current (ma) Lambda (nm) Near max. power Q8 Workshop CAM 7 July 6, p. 1

13 Beam profiles at.65 W Near-field at waist Far-field Optical Power (a.u.) µm FWHM 14. µm at 1/e.65 W 1. A Optical Power (a.u.) FWHM 4.8 at 1/e.65 W 1. A Position (µm) Angle ( ) M at 1/e < 1.4 M ss <.5 Angle ~ 5 at 1/e at.65w Q8 Workshop CAM 7 July 6, p. 13

14 Beam properties (slow axis) Evolution of apertures with current Evolution of M with current Width at 1/e (µm) Angle at 1/e ( ) M 3 1 M ss M at 1/e Current (A) Current (A) Low and stable angle of ~ 5 at 1/e M at 1/e < 1.4 M ss <.5 at.65 W Q8 Workshop CAM 7 July 6, p. 14

15 Interest for the Clarinet lasers for bars 5 5 Width at 1/e (µm) Current (A) Angle at 1/e ( ) IG1: Divergence increases with current 5 5 Width at 1/e (µm) Current (A) Angle at 1/e ( ) Clarinet: Divergence Stable with current Very advantageous for bars Q8 Workshop CAM 7 July 6, p. 15

16 Comparison of single emitters P( W) B = S( cm²). Ω( srd) P 1 = λ² M M // High P and Low M² // High B Structure Power M Brightness (W) at 1/e (MW/cm /sr) BA Laser Ridge* IG * Per facet Clarinet Highest B + narrowest q // Q8 Workshop CAM 7 July 6, p. 16

17 High power Laser structure Very low internal losses (a i <.5 cm -1 ) Very low J (86 A/cm ) P max = 7 W (AR/HR). At 5W, M² =18 at 1/e² B = 33 MW/cm²/sr High brightness on single emitters IG1 lasers 1. W at 1.5 A. At 1 W, M = 3. at 1/e B = 4 MW/cm²/sr Clarinet lasers < 1 HR Few tens.65 W at 1. A, M = 1.3 at 1/e² of B µm = 6 MW/cm²/sr Interest of low HR angles for bars Few tens AR 3 mm of µm Small IG1 lasers arrays and bars were realised q // = 6. FWHM, 1. at 1/e AR at 1 W 6xIG1 array: 4W 3 mm Clarinet lasers 6 mm bar (16 groups q // =.6 of FWHM, 4xIG1): 4.8 W at 1/e at.65 W Future work New laser structure with GaAlAs claddings Conclusions Q8 Workshop CAM 7 July 6, p. 17