Butterfly Package Research Articles

Sub-20 kHz low-frequency noise near ultraviolet butt-coupled fiber Bragg grating external cavity laser diode

We present a butt-coupled InGaN fiber Bragg grating (FBG) semiconductor laser diode operating below 400 nm in the single-mode emission regime. This compact coherent laser source exhibits an intrinsic linewidth of 14 kHz in the near-UV range and a side-mode suppression ratio reaching up to 40 dB accompanied by almost 2 mW output power. Furthermore, the properties of the FBG, including its central wavelength, bandwidth, and reflectivity, can be readily customized to fulfill specific requirements. As a result, the small footprint design of this laser is compatible with integration into a standard butterfly package to ease the lab-to-market technology transfer. The combination of low-frequency noise and fibered output signal positions these FBG laser systems as strong candidates for hybridization with integrated photonic platforms tailored for quantum information processing and metrology.

On Excess CO2 within a Hermetically Sealed 14-Pin Butterfly Package: Solubility of CO2 within Fluorocarbon Liquids

In this paper, we examine the presence of excess CO2 found within a hermetically sealed 14-pin butterfly package. Excess CO2 within a hermetically sealed package can suggest that the internal structures of the package have degraded significantly over the lifetime of the package. The level of CO2 discovered within the butterfly package was inconsistent with the controlled sealing gas environmental composition, and the gas composition of concurrently sealed packages. A literature review of industry technical papers and academic studies show that fluorocarbon liquids preferentially absorb CO2 at levels 4-5 times greater than other gasses such as oxygen and nitrogen. Previous experimental and computational methods found that fluorocarbon liquids can absorb CO2 at levels of 1.5-1.6 mol%, which is greater than the calculated maximum amount of absorbed CO2 (0.91 mol%) found within the butterfly package. The Internal Gas Analysis (IGA) of the butterfly package confirmed that it is highly likely that when butterfly package ingested the fluorocarbon liquid, the CO2 was absorbed in solution and thus ingested into the device. Given that the butterfly package was initially filled with 12% ppmv of helium and it retained the helium at a significant level, the phenomenon of a one-way leaker preserved the evidence of CO2 absorbed in the fluorocarbon liquid.

Development of small form factor packaged single-mode semiconductor laser for spectroscopic applications at 689 nm

We report on the development of a compact packaged semiconductor laser capable of spectroscopy applications at 689 nm. The key component is an optical isolator that is small enough to fit inside a package that is compatible with standard 14-pin butterfly packages. We present a threshold current of 33 mA, a forward voltage of 2.5 V at 50 mA, long term reliability study for over 12,500 h, a relative intensity noise below −145 dBc/Hz, and a linewidth of 1.4 MHz. The relative intensity noise and the frequency noise spectra verify continuous-wave lasing and frequency stability of the packaged laser.

Coupling efficiency of laser diode to GRIN fiber by aspherical lens

An optical coupling system consisting of a laser diode (LD), aspherical lens, and Graded-index (GRIN) fiber is experimentally constructed in butterfly packaging and theoretically simulated. The effects of incident wavelength, laser beam waist radius, lens thickness, GRIN radius, and positioning errors of optical components on coupling efficiency (CE) are systematically investigated. To achieve a large CE value in the GRIN fiber coupling system, the optical structures with appropriate parameters and positions are carefully adjusted in the experiment and simulation. The model coupling efficiency reached 85.5% when the lens and fiber endface losses are neglected, in line with an actual situation. The CE trends under misalignment and tolerance adjustments can be explained by the beam propagation theory and the light-gathering ability of the GRIN fiber. The study is useful in optimum launch optics for designing and fabricating GRIN fiber on coupled packaging of optoelectronic devices.

Coupling efficiency of a laser diode to a single-mode fiber via a microlens on the fiber tip

A conical microlens on the tip of a fiber for improving the coupling efficiency (CE) of a laser diode and a single-mode fiber in butterfly packaging was experimentally fabricated via the grinding and polishing method and theoretically designed using the beam propagation method. The CE, varying with working distance, was explored under all kinds of optical coupling system parameters, such as incident wavelength, laser beam waist radius, numerical aperture of the fiber, refractive index, and diameter of the microlens. The optimal working distance for the maximal CE was located at approximately 15 μm, proving that the conical-tip coupling was a tight packaging type. Therefore, the CE trends under misalignment and tolerance adjustments could be explained by the spherical aberration theory and light-gathering ability of the microlens. The results are useful in optimum launch optics for designing and fabricating microlens tips on coupled packaging of optoelectronic devices.

QEPAS sensor in a butterfly package and its application.

Molecular gases are highly relevant in healthcare, production control, safety, and environmental monitoring. They often appear in small concentrations. The measurement of trace gases has increasingly become a key technique in those domains. Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a suitable method that can provide the required low detection limits in such applications at comparatively low cost and small size. For mobile implementation, the size of an entire sensor unit matters. In this paper, we present a QEPAS sensor that fits into a standard butterfly package, its characterization, and its application on CH4 and CO2.

Butterfly-packaged multi-channel interference widely tunable semiconductor laser with improved performance.

A multi-channel interference (MCI) widely tunable semiconductor laser is described in detail with improved performance in this paper. The MCI laser without the common phase section was packaged into a standard 14-pin butterfly package. The device realized a tuning range of more than 40 nm with side mode suppression ratios (SMSRs) higher than 48 dB and about 7 dBm fiber power. By making the gain section and the phase sections to be surface ridge waveguides, threshold currents of the laser have become less than 18 mA across the tuning range. Besides, tuning characteristics of the MCI laser were experimentally studied in detail for the first time. The MCI laser can be treated as a combination of eight Fabry-Pérot (FP) cavity lasers which share the same gain section. It is found that when the eight arm phase sections are completely in phase at the lasing wavelength, the operating currents are at maxima of the output power curves. The relationship between the lasing wavelength and the injection currents of the eight arm phase sections has been introduced and analyzed.

Integrated turnkey soliton microcombs.

Optical frequency combs have a wide range of applications in science and technology1. An important development for miniature and integrated comb systems is the formation of dissipative Kerr solitons in coherently pumped high-quality-factor optical microresonators2-9. Such soliton microcombs10 have been applied to spectroscopy11-13, the search for exoplanets14,15, optical frequency synthesis16, time keeping17 and other areas10. In addition, the recent integration of microresonators with lasers has revealed the viability of fully chip-based soliton microcombs18,19. However, the operation of microcombs requires complex startup and feedback protocols that necessitate difficult-to-integrate optical and electrical components, andmicrocombs operating at ratesthat are compatible with electronic circuits-as isrequired in nearly all comb systems-have not yet been integrated with pump lasers because of their high power requirements. Here we experimentally demonstrate and theoretically describe a turnkey operation regime for soliton microcombs co-integrated with a pump laser. We show the appearance of an operating point at which solitons are immediately generated by turning the pump laser on, thereby eliminating the need for photonic and electronic control circuitry. These features are combined with high-quality-factor Si3N4 resonators to provide microcombs with repetition frequencies as low as 15 gigahertz that are fully integrated into an industry standard (butterfly)package, thereby offering compelling advantages for high-volume production.

Генерация пикосекундных импульсов лазерами с распределенной обратной связью с длиной волны 1064 nm

Picosecond optical pulses generation by 1064nm InGaAs/GaAs quantum well distributed feedback lasers was investigated. In the gain-switching regime the duration of laser pulses decreased from 150 to 35 ps with temperature increase from 5 to 50 degrees. The minimal pulses duration 35 ps and spectral width 70 pm was achieved in the optimal temperature range. The laser was placed in sealed butterfly package, which made it possible to obtain wavelength temperature tuning of 3 nm where the pulses duration was less than 45 ps. The output peak power was 0.4 W from single-mode polarization maintaining fiber.

Narrow-Strip 670 nm Gain-Coupled Distributed Feedback Laser Based on Periodic Anodes Fabricated by I-Line Lithography

A narrow-strip single-longitudinal-mode gain-coupled distributed feedback semiconductor laser with a central wavelength of approximately 670 nm is demonstrated. We fabricate a novel micro-scale regrowth-free gain-coupled grating with an island-like shape without nanoscale gratings by i-line lithography only. The maximum output power from the fiber of the device with butterfly package is 48.1 mW at 100 mA and its slope efficiency is 0.79 W/A. The laser can be continuously tuned from 670.750 to 670.784 nm with a side-mode suppression ratio of over 40 dB, covering the absorptive peak of lithium atoms. Our easily fabricated devices have great potential as light sources in many applications such as lithium atom detectors.

A Hybrid Integrated Short-External-Cavity Chaotic Semiconductor Laser

A simple design of a hybrid integrated short-external-cavity chaotic semiconductor laser module is presented and fabricated. A distributed feedback laser chip is directed to the transflective mirror through a collimating micro-lens, and a part of the light is reflected by the mirror into the laser chip to induce chaos. Transmitted through the mirror, the generated chaotic light is coupled into a pigtail fiber as output by a focusing micro-lens. It should be pointed out that the part between the transflective mirror and the emitting surface of the chip works as a short external straight feedback cavity. All the components above together with chip submount, heat sink, and thermoelectric cooler are encapsulated by a commercial 14-pin butterfly package. In our experimental fabrication, the intensity reflectivity of the transflective mirror is optimized as 5% and the external-cavity length is 2 mm. Experimental tests show that chaotic light with a bandwidth larger than 4.5 GHz is readily obtained from the chaotic laser module by adjusting laser bias current.

Ultra-wideband Butterfly Directly Modulated Semiconductor Lasers

In this paper, a simple and cost-effective packaging scheme for improving the modulation bandwidth of directly modulated laser is presented and demonstrated. Combined with the equivalent circuit, the effect of disequilibrium on signal injection efficiency is comprehensively and systematically studied. The simulation and measurement results have a good agreement, which show that the high frequency performance of module can be effectively improved with the proposed packaging scheme. Finally, employing the proposed packaging scheme, we achieve the 3-dB bandwidth of up to 32 GHz regarding the directly modulated semiconductor laser module with the butterfly package.

Butterfly packaged low‐linewidth optical comb source

A packaged optical comb source is demonstrated. A low-linewidth optical comb source is designed and fabricated. The device is packaged in a seven-pin high-speed butterfly package with an subminiature version A (SMA) connector for RF modulation and fibre pigtail. Fibre coupling efficiency is estimated at 43%. The packaged comb source is shown to have a linewidth of 300 kHz for the comb line set when modulated at 4 GHz, with eight comb lines within 3 dB of each other. The prototype packaged comb source has applications in high bandwidth telecommunications.

Miniaturised master‐oscillator power‐amplifier emitting a single longitudinal mode with more than 300 mW at 647 nm

A miniaturised red-emitting master-oscillator power-amplifier (MOPA) was developed. The MOPA emits a single longitudinal mode with a linewidth below 10 MHz and an optical output power of more than 300 mW at a wavelength of about 647 nm. The master-oscillator is a distributed-Bragg-reflector ridge-waveguide laser which provides the single mode with an output power of about 40 mW. The light is shaped by micro-lenses and guided through a miniaturised CdMnTe-Faraday isolator as well as a truncated tapered power amplifier; it is reshaped again afterwards to produce an almost circular, nearly diffraction-limited beam. The total length of the MOPA is below 50 mm, which fitted into a sealed butterfly package with a footprint of about 20 cm2.

Linewidth Measurement of Distributed-Feedback Semiconductor Lasers Operating Near 2.05 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>

The first unambiguous linewidth measurements are reported for fiber-pigtailed high-power distributed feedback (DFB) semiconductor lasers operating near 2.05 $\mu \text{m}$ wavelength range. The DFB lasers are packaged inside standard 14-pin butterfly package with polarization- maintaining output fiber and an integrated optical isolator. The Schawlow-Townes linewidth was measured using the coherent frequency-discriminator technique with a fiber Mach-Zehnder interferometer and the total linewidth was characterized using a heterodyne setup. Our measurements indicate less than 100 KHz Schawlow-Townes linewidth and a total linewidth of less than 200 KHz over 50 ms measurement time.

Butterfly packaged high‐speed and low leakage InGaAs quantum well photodiode for 2000nm wavelength systems

An edge-coupled high-speed photodiode based on strained InGaAs quantum wells for detection at 2000nm is demonstrated. The fabricated device shows a leakage current as low as 120nA at −3V bias voltage and a responsivity of around 0.3A/W at 2000nm. The high-speed butterfly packaging of the device is presented which shows a 3dB bandwidth of more than 10GHz. The device shows similar high-speed performance at 1550nm.

Integrated Two-Section Discrete Mode Laser

The authors present the design and characterization of a novel integrated two-section discrete mode index patterned diode laser source. The two slotted regions etched into the laser ridge waveguide are formed in the same fabrication step as the ridge, thus avoiding the requirement for complex lithography and regrowth steps. The laser is encased in a temperature-controlled butterfly package, which simplifies the static and dynamic measurements. Initial static characterization of this two-section laser shows that the injection, from the master laser to the slave laser, enhances the slave's emission side-mode suppression ratio from 30 dB to over 50 dB and its relative intensity noise is reduced from about -129.3 dB/Hz to -142.6 dB/Hz. Subsequent dynamic characterization then shows that the modulation bandwidth of the laser can be improved via injection to about three times the inherent free-running bandwidth. Hence, optical injection from master section into slave section enables the improvement of various parameters, which makes this two-section device attractive as a transmitter in optical communication systems.

43 Gb/s 1.3 $\mu$m DFB Laser for 40 km Transmission

We describe the performance of 1.3 $\mu$ m InGaAlAs ridge waveguide multiple quantum-well distributed feedback lasers. We obtained a 3 dB down bandwidth frequency of around 30 GHz by shortening the cavity length of the laser. We demonstrated experimentally that it is possible to obtain clear eye opening at a 43 Gb/s modulation speed after a 40 km single-mode fiber (SMF) transmission using a directly modulated laser. We fabricated a compact transistor outline (TO)-CAN module whose volume was about $1/19$ that of a conventional butterfly package. We successfully obtained clear eye opening for a 40 km SMF transmission at 43 Gb/s with the TO-CAN module.

103-Gb/s Long-Reach WDM PON Implemented by Using Directly Modulated RSOAs

We propose and demonstrate a long-reach wavelength-division-multiplexed passive optical network (WDM PON) capable of providing 100-Gb/s service to each subscriber, for the first time to the best of our knowledge. For cost-effectiveness, this network is implemented in loopback configuration by using directly modulated reflective semiconductor optical amplifiers (RSOAs) at 25.78 Gb/s. For the modulation of the RSOA at such a high-speed, we have to minimize the electrical parasitics by using the butterfly package. Also, to overcome the limited bandwidth of the RSOA, we utilize the electronic equalization technique at the receiver. We use four RSOAs at each optical network unit for the 103-Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free-spectral range of the cyclic arrayed waveguide gratings used at the central office and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM PON to be >; 120 km by using Erbium-doped fiber amplifiers at the RN. The results show that the error-free transmission can be achieved for all WDM channels in the wavelength range of >; 35 nm with sufficient power margins.

Directly Modulated Laser Diode Module Exceeding 10 Gb/s Transmission

A directly modulated laser diode module with over 10 Gb/s transmission and its performance, packaging process, and manufacturability are presented. The butterfly package consists of a V-connector, heat sink, and L-shaped microstrip line (MSL) which includes an integrated impedance matching resistor. The optical system consists of a 1.3- distributed feedback laser and a micro lens with isolator. A large modulation bandwidth of up to 15 GHz was obtained, and the eye diagram for 10 Gb/s modulation was clearly visible. Importantly, using an L-shaped MSL with integrated impedance matching resistor design, the module design is significantly simplified and can provide flexibility to insert various optical coupling systems. Moreover, since the laser was mounted directly on Kovar heat sink, optical output power reduction by thermal effects was 1 dB up to 50°C without active cooling. As a result of the simplified module configuration with flexibility, the module packaging process may be highly efficient for mass production.