RES E A R C H Open Access
Controlling the optical properties of a laser
pulse at λ = 1.55μm in InGaAs\InP double
coupled quantum well nanostructure
and Abdollah Malakzadeh
Background: The transient and steady-state behaviour of the absorption and the dispersion of a probe field
propagating at λ =1.55μm through an InGaAs\InP double coupled quantum well are studied. The effect of terahertz
signal excitation, electron tunnelling and incoherent pumping on the optical properties of the probe field is discussed.
Methods: The linear dynamical properties of the double coupled quantum well by means of perturbation theory and
density matrix method are discussed.
Results: We show that the group velocity of a light pulse can be controlled from superluminal to subluminal or vice
versa by controlling the rates of incoherent pumping field, terahertz signal and tunnelling between the quantum wells.
The required switching time is calculated and we find it between 3 to 15 ps.
Conclusions: In the terahertz (30 ~ 300 μm or 1 ~ 10THz) intersubband transition, the incoming photon energy is
(4 ~ 41mev) and maybe in the order of electron thermal broadening (KT ~ 6 meV-25 meV for 77 K -300 K). Therefore in
the conventional structure, the incoming photon can directly excite the ground state electrons to higher energy levels.
It is shown that the absorption and the dispersion of the probe field can be controlled by the intensity of terahertz
signal and incoherent pumping field.
Keywords: Electro-optical switching, Dispersion and absorption, Group velocity, Terahertz signal, Tunnelling effects,
Incoherent pumping field
It is known that the absorption and the dispersion
properties of a weak probe field can be modified effect-
ively by atomic coherence and quantum interference
[1–5]. Atomic coherence can be achieved by the strong
coupling fields, the spontaneous emission and incoher-
ent pumping fields. It is known that atomic coherence
due to the coherent laser field has essential roles for
modifying the optical properties of atomic systems such
as spontaneously generated coherence (SGC) , lasing
without inversion , modifying spontaneous emission
, coherent population trapping (CPT) , optical
bistability [6–10] and so on [11–16]. furthermore, it
has been shown that quantum interference arising from
SGC  and incoherent pumping field  can be used
for analyse of some interesting phenomena such as
lasing without population inversion , optical bistabil-
ity , and superluminal/subluminal light propagation
. Similar phenomena involving quantum coherence
in solid state systems such as semiconductor quantum
wells (QWs) and quantum dots (QDs) , can also be
occurred [20, 21]. In the past decade, there has been an
increasing interest in optical properties of quantum dot
molecules (QDMs) and quantum wells (QWs), due to
important role in optoelectronic devices. Recently, investi-
gators have examined the effects of an external field and
inter-dot tunnel coupling on the optical properties of QDs
and QWs [22–28]. Quantum well semiconductors were
* Correspondence: firstname.lastname@example.org
Young Researchers and Elite Club, North Tehran Branch, Islamic Azad
University, Tehran, Iran
Full list of author information is available at the end of the article
Journal of the European Optical
© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
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Shiri and Malakzadeh Journal of the European Optical
Society-Rapid Publications (2017) 13:19