Simulation of semiconductor modelocked ring lasers with monolithically integrated pulse shaping elements Martijn Heck, Yohan Barbarin, Erwin Bente Daan Lenstra Meint Smit Richard Nötzel, Xaveer Leijtens, Siang Oei Research Institute Technische Universiteit Eindhoven The Netherlands Supported by the Freeband program of the Dutch Ministery of Economic Affairs and the NRC Photonics Program of NWO COST Action 288 NUSOD 25 Berlin 22/9/25 1
Content Introduction to technology and motivation Modelocked ring laser model options for the realisation of a fs laser Modelocked ring laser bidirectional model NUSOD 25 Berlin 22/9/25 2
Optical Integrated Circuits in InP / InGaAsP Passive Waveguide Devices + Semiconductor Optical Amplifier + EO Phase Modulator InP InGaAsP (1.3) Loss 1dB/cm InP Light field Waveguide Passive components Active components Shallowly-etched Deeply-etched SOA or Sat. Abs. NUSOD 25 Berlin 22/9/25 3
Shallow waveguides Deeply etched waveguides 14 mm SOA Deeply etched AWG AWG Phase mod. NUSOD 25 Berlin 22/9/25 4
Passively modelocked lasers Modelocking using a reversely biased SOA section Slow saturable absorber modelocking Application: all optical clock recovery (4GHz) Ring laser configuration lithographic control of the cavity length injection locking combination with other components (e.g. all-optical switches) choose position of absorber gain section NUSOD 25 Berlin 22/9/25 5
Integrated femtosecond lasers Applications: Passively modelocked lasers Telecommunication THz bit rate communication Multi-wavelength ps source OCDMA source High speed optical ADC Pulses with controlled amplitude and phase Sensing, imaging, coherent control Approach: Dispersion control Self phase modulation compensating devices with(in) the laser Building blocks are available How do we put these together? NUSOD 25 Berlin 22/9/25 6
Modelling approach Model of modelocked ring laser AWG based integrated pulse shaping components Unidirectional ω / t Spectrum BW D AWG SOA SA MMI Round trip time Round trip time Spectrum ω / t Round trip time NUSOD 25 Berlin 22/9/25 7
Time domain: SOA Optical pulse description E ( t) P( t) exp( iω t iϕ( t) ) = Rate equations [J.M. Tang and K.A. Shore IEE Proc. Optoelectron, Vol 146, No. 1, 1999] s G =Γa N N = Γ 1 G N ( ) G G 1 G ε P 2 2 = + t τ E 1+ ε P s tr sat Iτ G anntr qvn 1 P Γ 2 β ' 2 tr P 2 ε 1 Non-linear gain compression carrier heating & spectral hole burning ε 2 Gain compression due to two photon absorption NUSOD 25 Berlin 22/9/25 8
SOA P and φ Power P G ε P = z 1+ ε 2 2 1 2 P 2Γ2β2 P αint 1P σ P Phase 1 ε GP ε P 2 φ = 1 2 α NG αt z 2 1+ ε1p Γ ' 2 ω c n 2 1 P σ α N Carrier density linewidth enhancement factor α T Carrier temperature linewidth enhancement factor n 2 Nonlinear refractive index NUSOD 25 Berlin 22/9/25 9
Q = Γa N NSA, trsa, Saturable Absorber Q Q Q 1 Q = t τ E 1+ ε Q P Q = z 1+ ε φ = z eff, SA sat, SA 1, SA 1 α 2 1, SA Q NSA, Q P P Effect of reverse bias on the diode in τ eff Ignored two photon absorption and fast non linear refraction. Phase change due to carrier heating is ignored. [Schell et al, IEEE J.QE, v32, p118, 1996] NUSOD 25 Berlin 22/9/25 1
Frequency domain: AWG, BW and D Optical pulse description MMI SOA DFT AWG BW E () t = E exp( iω t) n= Frequency filters (D) H n 2 ( ω ) = exp k" ( ω ω ) i 2 tot n SA D IDFT (AWG) NUSOD 25 Berlin 22/9/25 11
E Discrete Fourier Transform algorithm () t P() t exp ( iω t iϕ( t) ) E() t = E exp( iω t) = DFT n= n n MMI SOA SA AWG BW D IDFT Approximation valid when change per roundtrip is limited NUSOD 25 Berlin 22/9/25 12
Modeling the ring laser InP/InGaAsP active-passive (Q1.25/Q1.55) 4 GHz cavity 5% outcoupling 3nm system bandwidth Absorber CW Amplifier NUSOD 25 Berlin 22/9/25 13
Simulated pulse widths 8 k tot =.1ps 2, L SOA =5μm, L SA =5μm, α N =5, α T =3 Pulse width (ps) 7 6 5 4 3 2 small stability window @ τsa = 1-15ps self-phase modulation vs. gain dispersion open gain window trailing the pulse τ SA = 5ps 1ps 15ps 1 5 7 9 11 13 15 17 19 21 Injection current (ma) NUSOD 25 Berlin 22/9/25 14
Simulated pulse chirp.4.35.8.6 Power (W).3.25.2.15.1.5 -.5 Pulsewidths 1.5-2.ps 5 1 15 2 25-1 Time (ps) Upchirp of up to 2THz.4.2 -.2 -.4 upchirped pulses -.6 -.8 Chirp (THz) + dispersive element compression NUSOD 25 Berlin 22/9/25 15
Extracavity pulse compression 1.6 Pulse width (ps) 1.4 1.2 1.8.6.4.2 -.2 -.4 -.6 -.8-1 Dispersion k" (ps^2) -1.2 7 9 11 13 15 17 19 21 Injection current (ma) NUSOD 25 Berlin 22/9/25 16
IFSL concepts Proposed solutions for Integrated Femtosecond Semiconductor Lasers (IFSL) extracavity pulse compression breathing mode NUSOD 25 Berlin 22/9/25 17
Pulse compressor PHM AWG PHM PHM AWG MMI SOA SA NUSOD 25 Berlin 22/9/25 18
Discrete phase filter 2x2GHz 3 Phase (rad) 2 1-1 AWG channel transmission -2-3 -2-1.5-1 -.5.5 1 1.5 2 Frequency (THz) NUSOD 25 Berlin 22/9/25 19
AWG channel transmission 1.8 2GHz AWG channel spacing Gaussian flattened Transmission.6.4.2-2 -15-1 -5 5 1 15 2 Frequency (GHz) NUSOD 25 Berlin 22/9/25 2
Extracavity pulse compression FWHM 1.6ps 3fs 1 Gaussian.8 flattened Power (W).6.4 input pulse.4.2.1 5 1 15 2 25 Time (ps) NUSOD 25 Berlin 22/9/25 21
Realisation of compressor Martijn Heck Pascual Munoz (UPVLC - Valencia) NUSOD 25 Berlin 22/9/25 22
IFSL concepts Proposed solutions for Integrated Femtosecond Semiconductor Lasers (IFSL) extracavity pulse compression breathing mode Self-phase modulation gain dispersion instabilities minimize SPM! NUSOD 25 Berlin 22/9/25 23
Breathing mode configuration Compensate phase shift in SOA: to 2π Minimizes SPM in SOA Dispersive cavity Small stability regime t ω t ω t AWG 1 2 SOA SOA PHM PHM AWG N SOA PHM SA MMI Bandwidth: #channels x channel spacing NUSOD 25 Berlin 22/9/25 24
.18.16 Breathing mode 6 x 4GHz, τ abs =15ps Pulse power 1 Power (W).14.12.1.8.6.4 45fs pulses @ 4GHz.5 Δφ SOA = -Δφ PHM during start-up no self-starting! -.5 Chirp (THz) decrease τ SA from 15ps to 5ps.2 5 1 15 2 25-1 Time (ps) M2 NUSOD 25 Berlin 22/9/25 25
Breathing mode 6 x 4GHz, τ abs =5ps.7.6.5 Power (W).4.3.2.1 5 1 15 2 25 Time (ps) NUSOD 25 Berlin 22/9/25 26
Multi-wavelength ps pulse source Power (W).2.18.16.14.12.1.8.6.4.2 5 1 15 2 25 Time (ps) MWL pulse source FWHM 6ps 6 colors@4ghz synchronised -6GHz +2GHz +1GHz NUSOD 25 Berlin 22/9/25 27
All-active 15GHz Ring MLL 15GHz ring cavity with adiabitic bends 5µm SA Directional coupler Angled facet output + AR coating NUSOD 25 Berlin 22/9/25 28
15GHz Ring MLL results optical spectrum V=-1.6V I=145mA 6dB Linewidth: 2 MHz at -2dB optrical power (W).12.1.8.6.4.2 optrical power (dbm) -25-3 -35-4 -45-5 -55-6 152 1525 153 1535 154 (nm) 4.5 nm 152 1525 153 1535 154 (nm) Simulation 3.3 ps pulse width 1.2THz detuning 4.5nm bandwidth NUSOD 25 Berlin 22/9/25 29
Bidirectional model Ring divided in 25 fs segments Reflections No phase equation No TPA and gain compression G N =ΓaNNtr ln Ntr NUSOD 25 Berlin 22/9/25 3
The spectral bandwidth 14 elements Output filter = f (x n ) A Bessel digital filter is used: Numerically stable The transmission is similar to the measured SOA gain spectrum. NUSOD 25 Berlin 22/9/25 31
Positioning of the absorber CCW CW CCW CW Absorber Amplifier Absorber Amplifier NUSOD 25 Berlin 22/9/25 32
Evolution of the pulses in the cavity Absorber CCW Amplifier CW NUSOD 25 Berlin 22/9/25 33
26 GHz ring laser result Modelocked 26GHz ring laser by Y. Barbarin et al. IEEE PTL, publ. Nov 25 NUSOD 25 Berlin 22/9/25 34
Further development Two directional model phase equations and nonlinear effects (amp. And abs.) no intra-cavity reflections.6 4GHz ring 1 segments 14th order digital bandwidth filter 7 µm long amplifier 2µm long SA ICW j ICCW j.4.2 22 44 66 88 1.1. 1 4 T ICW j.5 Phase_CW j.2.4.2 Result for I amp =175mA and T abs = 15ps Power and Phase v.s. time Pulse width v.s. time after start-up.2 4773 4783 4793 483 4813 4823 Time in ps 8. 1 12 2 7. 1 12 6. 1 12 5. 1 12 31 4. 1 12 32 3. 1 12 2. 1 12 Time in ps 1.35 ps 1. 1 12 2 2 3 4 5 6 7 8 Time in ps NUSOD 25 Berlin 22/9/25 35
Conclusions Set up simulation tools for designing integrated modelocked lasers Simulations point a way to integrated fs laser systems Modelocked laser plus compressor Separate amplification of spectral components In a ring the power ratio in the two directions can be controlled through the relative position of the amplifier and absorber We have started to use the models: to design laser system to analyse results obtained with devices NUSOD 25 Berlin 22/9/25 36
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