Abstract

We report a novel chaos semiconductor laser chip in which a distributed feedback (DFB) laser, two semiconductor optical amplifiers (SOAs) and a photodiode (PD) are monolithically integrated with a passive ring waveguide. The ring-type structure with the two separate SOAs achieves stronger delayed optical feedback compared to previous chaos laser chips which use linear waveguide and facet-reflection. The integrated PD allows efficient detection of the optical signal with low optical loss. A rich variety of dynamical behaviors and optical signals can be selectively generated via injection currents to the two separate SOAs. In particular, the strong optical feedback makes possible the generation of strong broadband optical chaos, with very flat spectrum of ±6.5 dB up to 10 GHz. The stability and quality of the chaotic mode is demonstrated using strict statistical tests of randomness applied to long binary sequences extracted by sampling the optical intensity signal.

© 2011 Optical Society of America

Full Article  |  PDF Article

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.


Figures (11)

Fig. 1
Fig. 1

Device structures. (a)A schematic and (b)a photograph of the chaos laser chip.

Fig. 2
Fig. 2

The layer structures of the cross section in (a)the active region (DFB, SOAs, PD), and (b)the passive region. The grating is fabricated only for DFB part. MQW, multi-quantum well; W, ridge width; H, ridge height.

Fig. 3
Fig. 3

L-I characteristics for ridge height 1.8 μm (the red curve) and 1.7μm (the blue curve). The threshold current Jth is estimated to be 13mA.

Fig. 4
Fig. 4

Schematic of a test device used for the gain measurement. DFB, SOA, and two PDs (PD1 and PD2) are monolithically integrated with a passive waveguide (Passive WG), and the width of the waveguide is the same as that of the chaos laser chip.

Fig. 5
Fig. 5

Biasing current dependences of the gain for 200μm-long SOA (a) and 100μm-long SOA (b). DFB current is fixed at 22mA (about 1.7times of the threshold current).

Fig. 6
Fig. 6

Optical feedback power ratios vs. the injection currents to SOA1. The injection currents to SOA2 were fixed to 0 mA(blue curve), 3 mA(green curve), and 6 mA(red curve).

Fig. 7
Fig. 7

Experimental setup for measuring chaotic waveforms.

Fig. 8
Fig. 8

The waveforms of the PD signals for JSOA1= (a)6 mA, (b)7 mA, (c)8 mA, (d)9 mA, (e)12 mA, (f)15 mA.

Fig. 9
Fig. 9

The radio-frequency spectra for JSOA1= (a)6 mA, (b)7 mA, (c)8 mA, (d)9 mA, (e)12 mA, (f)15 mA.

Fig. 10
Fig. 10

(a) Autocorrelation of the chaotic signals obtained for JDFB = 22 mA, JSOA1 = 15 mA, and JSOA2 = 6 mA. (b) Enlargement of the short-time autocorrelation.

Fig. 11
Fig. 11

Schematic diagram for random bit generation.

Tables (2)

Tables Icon

Table 1 Results of NIST Special Publication 800-22(rev. 1a) statistical tests. The tests have been performed using 1000 samples of 1 Mbit data and significance level α = 0.01. For the tests which produce multiple P-values and proportions, the worst case is shown

Tables Icon

Table 2 Typical results of “Diehard” statistical test suite. KS - Kolmogorov-Smirnov test. Significance level “α = 0.01”. For tests with multiple p-value, the worst case is shown

Equations (2)

Equations on this page are rendered with MathJax. Learn more.

G = 1 T ap 2 P out P in .
P f = G 1 G 2 T ap 6 exp ( α p L p α pd L pd ) ,

Metrics