This paper presents the development and characterization of quantum-dot (QD) lasers grown directly on silicon, achieving ultra-low noise and narrow linewidth under external cavity locking (ECL). The QD lasers offer a scalable and cost-effective integration platform for high-coherence applications, such as optical sensing and signal generation. Key findings include: 1. **High-Performance QD Lasers**: The QD lasers exhibit low linewidth enhancement factor (LEF), resulting in narrow linewidth and frequency stability. They achieve a 16 Hz Lorentzian linewidth under ECL using a low-Q external cavity, outperforming conventional quantum-well (QW) lasers by four orders of magnitude in frequency noise reduction. 2. **Chaos-Free Operation**: The QD lasers operate chaos-free, enabling linewidth locking without the need for a frequency filter. This is in contrast to QW lasers, which require a high-Q external cavity to suppress coherence collapse. 3. **Turnkey Locking**: The QD lasers can be locked to a low-Q external cavity without power penalty, providing a more practical and robust solution compared to self-injection locking (SIL) lasers, which often require high-Q external cavities and careful tuning. 4. **Performance Comparison**: The QD lasers outperform conventional QW lasers in terms of linewidth and frequency noise reduction, making them suitable for applications requiring precise coherence, such as optical frequency synthesizers and ultra-high-capacity optical transceivers. 5. **Future Prospects**: The QD lasers are compatible with CMOS-ready high-Q microresonators, enabling further linewidth reduction to the sub-hertz level. The work also highlights the potential for monolithic integration of III-V lasers and passive waveguides onto a single chip, advancing the development of QD lasers for practical photonic applications. Overall, this study demonstrates the potential of QD lasers in achieving high-coherence and low-noise performance, making them a promising candidate for various advanced photonic applications.This paper presents the development and characterization of quantum-dot (QD) lasers grown directly on silicon, achieving ultra-low noise and narrow linewidth under external cavity locking (ECL). The QD lasers offer a scalable and cost-effective integration platform for high-coherence applications, such as optical sensing and signal generation. Key findings include: 1. **High-Performance QD Lasers**: The QD lasers exhibit low linewidth enhancement factor (LEF), resulting in narrow linewidth and frequency stability. They achieve a 16 Hz Lorentzian linewidth under ECL using a low-Q external cavity, outperforming conventional quantum-well (QW) lasers by four orders of magnitude in frequency noise reduction. 2. **Chaos-Free Operation**: The QD lasers operate chaos-free, enabling linewidth locking without the need for a frequency filter. This is in contrast to QW lasers, which require a high-Q external cavity to suppress coherence collapse. 3. **Turnkey Locking**: The QD lasers can be locked to a low-Q external cavity without power penalty, providing a more practical and robust solution compared to self-injection locking (SIL) lasers, which often require high-Q external cavities and careful tuning. 4. **Performance Comparison**: The QD lasers outperform conventional QW lasers in terms of linewidth and frequency noise reduction, making them suitable for applications requiring precise coherence, such as optical frequency synthesizers and ultra-high-capacity optical transceivers. 5. **Future Prospects**: The QD lasers are compatible with CMOS-ready high-Q microresonators, enabling further linewidth reduction to the sub-hertz level. The work also highlights the potential for monolithic integration of III-V lasers and passive waveguides onto a single chip, advancing the development of QD lasers for practical photonic applications. Overall, this study demonstrates the potential of QD lasers in achieving high-coherence and low-noise performance, making them a promising candidate for various advanced photonic applications.