Optical Bistability in Monolithic Two-sectioned InAs/InP

Quantum-dash Laser

E. Alkhazraji

1,2

, Mohd Sharizal Alias

and M. Z. M. Khan

Department of Electrical and Electronic Engineering Technology, Jubail Industrial College, Jubail 31961, Saudi Arabia

Optoelectronics Research Laboratory, Electrical Engineering Department, King Fahd University of Petroluem and

Minerals, Dhahran 31261, Saudi Arabia

Photonics Laboratory, Computer, Electrical and Mathematical Science and Engineering Division, King Abdullah

University of Science and Technology, Thuwal 23955-6900, Saudi Arabia

Keywords: Broadband Laser, Optical Bistability, Quantum Dash Laser, Two-section Laser.

Abstract: Observation of optical bistability in a two-section InAs/InP quantum dash laser is reported. The hysteresis in

the optical power-injection current (L-I) characteristics is found to vary with the absorber reverse bias

condition. A reverse bias of −0.8 (0) V to the saturable absorber, a hysteresis of 32 (24) mW is measured

when the injection current through the gain section is swept forward and backward. Moreover, the bistability

is further affirmed through investigation of the lasing emission spectra at specific operating points.

1 INTRODUCTION

Optical bistability in lasers has gained attraction in

several applications such as optical modulation, fast

optical switching, next generation optical networks,

and memory elements in optical circuits. Bistable

lasers come in different shapes and forms such as

external cavity lasers and fiber lasers (Kawaguchi,

2006; Huang, 2001; Tangdiongga, 2005; Qasaimeh,

1999; Feng, 2010). However, achieving bistability in

monolithic semiconductor lasers would be a much

more desirable alternative in terms of flexibility, cost,

compactness, and integrability (Kawaguchi, 2006;

Huang, 2001). A two-sectioned laser diode is one

configuration where both power (optical) and

wavelength bistability can be observed

(Tangdiongga, 2005; Qasaimeh, 1999; Feng, 2010).

Power stability is referred to the exhibited

hysteresis when the injection current is swept in

upward and downward directions which has been

investigated over a two-sectioned quantum dot laser

in (Huang, 2001), emitting at 1300 nm in the O-band

window.

In this report, we investigate the optical bistability

of a two-sectioned InAs/InP quantum dash laser diode

based on a highly inhomogeneous chirped barrier

thickness structure and emitting around in the L-band.

The power bistability is investigated by analyzing the

hysteresis observed in the L-I curves under specific

biasing conditions over the two separate sections.

Thereafter, the wavelength bistability is examined

through the emission spectra of the device under

different significant operating points. To the authors’

knowledge this is the first observation of bistability in

InAs/InP quantum dash lasers.

2 EXPERIMENTAL SETUP

Figure 1(a) illustrates the four-stack 930-μm long

InAs/InP quantum-dash laser diode (Qdash LD) that

has been electrically isolated by etching a portion of

the top metal contact resulting in an electrical

resistance of ~0.4–0.6 kΩ. The resulting two sections

are 600- and 330-μm long where the former is to be

used as a gain medium while the latter as a saturable

absorber.

The active medium of the Qdash LD in hand has

been chirped by varying its barrier layer thickness

atop each of its four quantum dash layers of. A more

detailed description of the structure can be found

elsewhere (Alkhazraji, 2018). Nevertheless, owning

to this chirped structure, in addition to the inherent

inhomogeneous nature of the self-assembled growth

process of quantum dashes, the structure

demonstrates ultra-broadband emission spectra

Alkhazraji, E., Alias, M. and Khan, M.

Optical Bistability in Monolithic Two-sectioned InAs/InP Quantum-dash Laser.

DOI: 10.5220/0007365100360038

In Proceedings of the 7th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2019), pages 36-38

ISBN: 978-989-758-364-3

qualifying it as a potent tunable laser source in its

emission window in the L-band (~1600 nm)

wavelength region.

In order to investigate the power bistability of the

two-sectioned Qdash LD, the gain section (GS) was

current-injected with a pulsed forward biasing current

signal of a duty cycle of 0.2% and pulse width of 500

ns to minimize the temperate effects. Meanwhile, the

absorber section (AS) was revers-biased with a

continuous wave voltage signal. The bare Qdash LD

was probed as such while mounted over a brass base

whose temperature was controlled by a

thermoelectric cooler.

3 RESULTS AND DISCUSSION

The L-I characteristics curves of the Qdash LD were

obtained by sweeping the injected current through the

GS (𝐼

𝑔

) under different reverse biasing voltages (𝑉

𝑅𝐵

)

across the AS at a constant temperature of 18

Figures 1 (b) and (c) show the L-I curves at 𝑉

𝑅𝐵

of 0

V and -0.8 V, respectively, where the output power

was measured from the AS facet. Figures 1 (b) and (c)

clearly show the optical bistability witnessed by this

structure as evident by the counter-clockwise

hysteresis loops when 𝐼

𝑔

is swept in forward then

backward directions. The insets of the Figures 1 (b)

and (c) show close-up images of the hysteresis loops

and their four corners depicted by the points A, B, C

and D.

Furthermore, not only did higher 𝑉

𝑅𝐵

values result

in shifting the hysteresis loop’s position to a higher

current injection value, possibly due to the associated

higher absorption coefficient, but also, they resulted

in a more optical bistable behaviour. This is shown by

the 24-mW hysteresis value exhibited under 𝑉

𝑅𝐵

0 𝑉 whereas the case of 𝑉

𝑅𝐵

= −0.8 𝑉 resulted in a

wider 32-mW hysteresis. This optical power

bistability could be potentially exploited in switching

operations by optimally biasing the Qdash LD at the

middle of the hysteresis loops while direct

modulation or on-off switching would be achieved by

positively and negatively pulsed-current injecting the

GS.

Moreover, in the contrary to other devices, the

power bistability is observed here by merely reverse

biasing the AS without the need of any additional

components such as resistive loads as has been done

in the case of the specimen reported in (Qasaimeh,

1999).

From a wavelength bistability point of view,

Figure 2 shows the emission spectra of the Qdash LD

(a)

Figure 1: (a) Illustration of the two-sectioned chirped

quantum dash laser diode. The LI characteristics curves

showing the power bistability under a reverse bias voltage

of (b) 0 V and (c) -0.8V. The insets show a close-up image

of the corners of the hysteresis loops.

at the corners of the hysteresis loop under a fixed

reverse bias voltage of 𝑉

𝑅𝐵

= −0.8 𝑉 at points A, B,

C, and D that have been discussed earlier. The y-axis

optical power is in offset arbitrary units. As expected

from the L-I curves shown in Figures 2 (b) and (c) in

Optical Bistability in Monolithic Two-sectioned InAs/InP Quantum-dash Laser

particular, each pair of (A, B) and (D, C) points shows

a higher emission bandwidth, longer central

wavelength, and more integrated power when the

forward path points, A and D, are compared to the

backward path ones, B and C. This behaviour

suggests that achieving stimulated emission with

broad emission near threshold is potentially more

easily attainable in such two-sectioned

inhomogeneous and dissimilarly biased structures

compared to single section devices which can

attributed to their different gain profiles (Swertfeger,

2017).

Figure 2: Emission spectra at the corners of the hysteresis

loop of the Qdash LD at a fixed reverse bias voltage of

-0.8V across the AS at points A, B, C, and D. The y-axis

optical power is in offset arbitrary units.

4 CONCLUSION

The observation of optical and wavelength bistability

of a two-sectioned multi-stacked chirped InAs/InP

quantum-dash laser diode has been further

investigated. The two-sectioned device showed

power bistability when one of the sections is revers

biased and was shown in the form of counter-

clockwise hysteresis loops that get wider and elevated

with higher current injections in the gain section and

when the reverse biasing voltage across the absorber

section increases.

As such, a hysteresis of 32 mW was observed

under a reverse bias of −0.8 V. This behavior could

be potentially utilized in on-off switching and direct

modulation and could be further improved by further

optimization of the growth process and the

geometrical dimensions of the laser device.

ACKNOWLEDGEMENTS

This work was supported by King Fahd University of

Petroleum and Minerals through IN161029 grant.

M. Z. M. K gratefully acknowledges contributions

from Prof. B. S. Ooi and Dr. T. K. Ng from King

Abdullah University of Science and Technology

(KAUST), and Prof. P. Bhattacharya, and Dr. C-S.

Lee from University of Michigan.

REFERENCES

H. Kawaguchi, T. Mori, Y. Sato, and Y. Yamayoshi, 2006.

Optical buffer memory using polarization-bistable

vertical-cavity surface-emitting lasers. In J. Appl. Phys,

vol. 45, no. 33–36, p. L894.

Xiaodong Huang et al., 2001. Bistable operation of a two-

section 1.3 /spl mu/m InAs quantum dot laser-

absorption saturation and the quantum confined Stark

effect". In IEEE Journal of Quantum Electronics, vol.

37, no. 3, pp. 414-417.

E. Tangdiongga, X. L. Yang, Z. G. Li, Y. Liu, D. Lenstra,

G. D. Khoe, and H. J. S. Dorren, 2005. Optical flip-flop:

Based on two-coupled modelocked ring lasers. In IEEE

Photon. Technol. Lett., vol. 17, no. 1, p. 208.

O. Qasaimeh, W. D. Zhou, J. Philips, S. Krishna, P.

Bhattacharya, and M. Dutta, 1999. Bistability and self-

pulsation in quantum-dot lasers with intracavity

quantum-dot saturable absorbers. In J. Appl. Phys. Lett.,

vol. 74, no. 12, pp. 1654–1656.

M. Feng, S. T. Cundiff, R. P. Mirin and K. L. Silverman,

2010. Wavelength Bistability and Switching in Two-

Section Quantum-Dot Diode Lasers. In IEEE Journal

of Quantum Electronics, vol. 46, no. 6, pp. 951-958.

E. Alkhazraji, M.T.A. Khan, A.M. Ragheb, H. Fathallah,

K.K. Qureshi, S. Alshebeili, M.Z.M. Khan, 2018.

Effect of temperature and ridge-width on the lasing

characteristics of InAs/InP quantum-dash lasers: A

thermal analysis view. In Optics & Laser Technology,

Vol. 98, pp. 67-74.

Swertfeger R., Beil J., Misak S., Thomas J., Campbell J.,

Renner D., Mashanovitch M. and Leisher P, 2017.

Direct Observation of the 2D Gain Profile in High

Power Tapered Semiconductor Optical Amplifiers. In

Proceedings of the 5th International Conference on

Photonics, Optics and Laser Technology –

PHOTOPTICS , pp. 114-121.

PHOTOPTICS 2019 - 7th International Conference on Photonics, Optics and Laser Technology