Semiconductor optical gain

About: Semiconductor optical gain is a research topic. Over the lifetime, 5997 publications have been published within this topic receiving 96505 citations.

Importance of self-induced carrier-density modulation in semiconductor lasers

Abstract: Semiconductor lasers have a built-in mechanism for modulating the carrier density at multiples of the longitudinal-mode spacing. This mechanism is believed to be relatively unimportant for solitary laser diodes since the mode spacing typically exceeds 50 GHz. A general numerical model capable of including self-saturation, cross saturation, and four-wave mixing occurring due to both interband and intraband effects is presented, and the self-induced carrier-density modulation is shown to play an important role in solitary laser diodes. In particular, it can severely degrade the gain margin and the mode-suppression ratio in single-mode semiconductor lasers when the operating current is increased. Degradation depends on the linewidth enhancement factor and the laser length and can be especially severe when the cavity length exceeds 1 mm. >

Optical semiconductor device and optical semiconductor integrated circuit

Abstract: An optical semiconductor device in which a combination of materials of different refractive indices and temperature dependences of the refractive indices is used and an optical integrated circuit are disclosed. Especially, the temperature dependence of the oscillation wavelength can be controlled by a propagation region having a material and/or structure different in the temperature dependence of refractive index from that of the gain region of a semiconductor laser. An optical waveguide can have a structure in which interfaces are formed along the light guiding direction, and light reflected from a first interface is weakened by the light reflected from other interfaces. Further, by disposing the interfaces at angles with respect to the light propagation direction, the waveguide loss due to reflection and refraction between optical waveguides of different refractive indices can be reduced.

An infinite order perturbation approach to gain calculation in injection semiconductor lasers

Abstract: Nonlinear gain in injection semiconductor lasers is analyzed by applying an infinite order perturbation treatment to the density matrix analysis and taking in account the electron relaxation processes in single-mode operation. The infinitely expanded gain can be applied to future laser developments having much lower threshold current. Formulas for linear and higher orders of the expanded density matrix element and for their corresponding orders of the gain coefficient are investigated. The infinitely expanded gain is obtained in closed form which, in general, cannot be handled analytically. This closed form is simplified in the simple case of plane-wave fields and is approximated to the previously reported gain formulas within limits of perfectly homogeneous and inhomogeneous gain broadening. Numerical examples are given for the case of GaAs lasers having a specified intraband relaxation time. Based on these numerical results, simplified expressions are presented for linear and higher orders of the gain coefficient in terms of the injected carrier number. Furthermore, numerical criteria to truncate the infinite gain expansion for different higher orders are investigated based on the values of the lasing power. In the case of conventional semiconductor lasers, where the injection current is up to three times its threshold value, the third-order gain expansion corresponds to the infinitely expanded gain. However, the fifth-order expansion gives a more accurate description at higher current up to ten times the threshold. More exact gain analysis at higher ranges of the injection current requires higher orders in the gain expansion.

Light source apparatus and its control method

Abstract: A light source apparatus capable of realizing stable higher harmonic even when the ambient temperature is changed or the output power fluctuates. The light source apparatus includes a semiconductor laser light source (4), an optical waveguide type QPM-SHG device (5) generating a second higher harmonic from the light emitted from the semiconductor laser light source (4), wavelength control means (7) for controlling the wavelength of the light emitted from the semiconductor laser light source (4), wavelength fine fluctuation means (8) for changing the wavelength of the light emitted from the semiconductor laser light source (4), and means for detecting a change of the output light power of the optical waveguide type GPM-SHG device (5) when the wavelength of the light emitted from the semiconductor laser light source (4) is changed. In this case, according to the change of the output light power of the optical waveguide type GPM-SHG device (5) when the wavelength of the light emitted from the semiconductor laser light source (4) is changed, the wavelength of the light emitted from the semiconductor laser light source (4) is controlled so as to be optimal for the optical waveguide type QPM-SHG device (5).

Large inherent optical gain from the direct gap transition of Ge thin films

Abstract: The recent demonstration of Ge-on-Si diode lasers renews the interest in the unique carrier dynamics of Ge involving both direct (Γ) and indirect (L) valleys. Here, we report a large inherent direct gap optical gain ≥1300 cm−1 at room temperature from both tensile-strained n+ Ge-on-Si films and intrinsic Ge-on-insulator using femtosecond transmittance spectroscopy captured before direct-to-indirect valley scattering. This inherent direct gap gain is comparable to III-V semiconductors. For n+ Ge, this transient gain is ∼25× larger than its steady state gain, suggesting that reducing Γ→L or enhancing L→Γ intervalley scattering may significantly increase the optical gain of Ge lasers.