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Temperature invariant output slope efficiency and threshold current ͑T 0 = ϱ͒ in the temperature range of 5-75°C have been measured for 1.3 µm p-doped self-organized quantum dot lasers. Similar undoped quantum dot lasers exhibit T 0 = 69 K in the same temperature range. A self-consistent model has been employed to calculate the various radiative and nonradiative current components in p-doped and undoped lasers and to analyze the measured data. It is observed that Auger recombination in the dots plays an important role in determining the threshold current of the p-doped lasers.

A platform for the realization of tightly-confined lithium niobate photonic devices and circuits on silicon substrates is reported based on wafer bonding and selective oxidation of refractory metals. The heterogeneous photonic platform is employed to demonstrate high-performance lithium niobate microring optical resonators and Mach-Zehnder optical modulators. A quality factor of ~7.2 × 10⁴ is measured in the microresonators, and a half-wave voltage-length product of 4 V.cm and an extinction ratio of 20 dB is measured in the modulators.

Compact electro-optical modulators are demonstrated on thin films of lithium niobate on silicon operating up to 50 GHz. The half-wave voltage length product of the high-performance devices is 3.1 V.cm at DC and less than 6.5 V.cm up to 50 GHz. The 3 dB electrical bandwidth is 33 GHz, with an 18 dB extinction ratio. The third-order intermodulation distortion spurious free dynamic range is 97.3  dBHz^2/3 at 1 GHz and 92.6  dBHz^2/3 at 10 GHz. The performance demonstrated by the thin-film modulators is on par with conventional lithium niobate modulators but with lower drive voltages, smaller device footprints, and potential compatibility for integration with large-scale silicon photonics.

The modulation bandwidth of conventional 1.0-1.3 µm self-organized In(Ga)As quantum dot (QD) lasers is limited to ∼6-8 GHz due to hot carrier effects arising from the predominant occupation of wetting layer/barrier states by the electrons injected into the active region at room temperature. Thermal broadening of holes in the valence band of QDs also limits the performance of the lasers. Tunnel injection and p-doping have been proposed as solutions to these problems. In this paper, we describe high-performance In(Ga)As undoped and p-doped tunnel injection self-organized QD lasers emitting at 1.1 and 1.3 µm. Undoped 1.1 µm tunnel injection lasers have ∼22 GHz small-signal modulation bandwidth and a gain compression factor of 8.2 × 10 −16 cm 3. Higher modulation bandwidth (∼25 GHz) and differential gain (3 × 10 −14 cm 2) are measured in 1.1 µm p-doped tunnel injection lasers with a characteristic temperature, T 0 , of 205 K in the temperature range 5-95˚C. Temperature invariant threshold current (infinite T 0) in the temperature range 5-75˚C and 11 GHz modulation bandwidth are observed in 1.3 µm p-doped tunnel injection QD lasers with a differential gain of 8 × 10 −15 cm 2. The linewidth enhancement factor of the undoped 1.1 µm tunnel injection laser is ∼0.73 at lasing peak and its dynamic chirp is <0.6 Å at various frequencies and ac biases. Both 1.1 and 1.3 µm p-doped tunnel injection QD lasers exhibit zero linewidth enhancement factor (α ∼ 0) and negligible chirp (<0.2 Å). These dynamic characteristics of QD lasers surpass those of equivalent quantum well lasers.